Chapter 49 Lecture : Chapter 49 Lecture Sensory and motor function
Slide2 : CHAPTER 49 SENSORY AND MOTOR SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A: Sensing, Acting, and Brains 1. The brain’s processing of sensory input and motor output is cyclical rather than linear
1. The brain’s processing of sensory input and motor output is cyclical rather than linear : The way it ISN’T: sensing brain analysis action.
The way it is: sensing, analysis, and action are ongoing and overlapping processes.
Sensations begin as different forms of energy that are detected by sensory receptors.
This energy is converted to action potentials that travel to appropriate regions of the brain.
The limbic region plays a major role in determining the importance of a particular sensory input. 1. The brain’s processing of sensory input and motor output is cyclical rather than linear Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide4 : CHAPTER 49 SENSORY AND MOTOR SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section B: Introduction To Sensory Reception 1. Sensory receptors transduce stimulus energy and transmit signals to the nervous system
2. Sensory receptors are categorized by the type of energy they transduce
Slide5 : Sensations are action potentials that reach the brain via sensory neurons.
Perception is the awareness and interpretation of the sensation. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
1. Sensory receptors transduce stimulus energy and transmit signals to the nervous system : 1. Sensory receptors transduce stimulus energy and transmit signals to the nervous system Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.2
Slide7 : Sensory reception begins with the detection of stimulus energy by sensory receptors.
Exteroreceptors detect stimuli originating outside the body.
Interoreceptors detect stimuli originating inside the body.
Sensory receptors convey the energy of stimuli into membrane potentials and the transmit signals to the nervous system.
This involves: sensory transduction, amplification, transmission, and integration. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide8 : Sensory Transduction.
The conversion of stimulus energy into a change in membrane potential.
Receptor potential: a sensory receptor’s version of a graded potential. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide9 : Amplification.
The strengthening of stimulus energy that is can be detected by the nervous system.
May be a part of, or occur apart from, sensory transduction. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide10 : Transmission.
The conduction of sensory impulses to the CNS.
Some sensory receptors must transmit chemical signals to sensory neurons.
The strength of the stimulus and receptor potential affects the amount of neurotransmitter released by the sensory receptor.
Some sensory receptors are sensory neurons.
The intensity of the receptor potential affects the frequency of action potentials. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide11 : Integration.
The processing of sensory information.
Begins at the sensory receptor.
For example, sensory adaptation is a decrease in responsiveness to continued stimulation.
For example, the sensitivity of a receptor to a stimulus will vary with environmental conditions. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
2. Sensory receptors are categorized by the type of energy they transduce : 2. Sensory receptors are categorized by the type of energy they transduce Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.3
Slide13 : Mechanoreceptors respond to mechanical energy.
For example, muscle spindles is an interoreceptor that responds to the stretching of skeletal muscle.
For example, hair cells detect motion. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide14 : Pain receptors = nocioceptors.
Different types of pain receptors respond to different types of pain.
Prostaglandins increase pain by decreasing a pain receptors threshold.
Anti-inflammatories work by inhibiting prostaglandin synthesis. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide15 : Thermoreceptors respond to heat or cold.
Respond to both surface and body core temperature. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide16 : Chemoreceptors respond to chemical stimuli.
General chemoreceptors transmit information about total solute concentration.
Specific chemoreceptors respond to specific types of molecules.
Internal chemoreceptors respond to glucose, O2, CO2, amino acids, etc.
External chemoreceptors are gustatory receptors and olfactory receptors. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide17 : Electromagnetic receptors respond to electromagnetic energy.
Photoreceptors respond to the radiation we know as visible light.
Electroreceptors: some fish use electric currents to locate objects. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide18 : CHAPTER 49 SENSORY AND MOTOR SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section C: Photoreceptors And Vision 1. A diversity of photoreceptors has evolved among invertebrates
2. Vertebrates have single-lens eyes
3. The light-absorbing pigment rhodopsin triggers a signal-transduction pathway
4. The retina assists the cerebral cortex in processing visual information
Slide19 : Most, if not all, animal photoreceptors may be homologous. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
1. A diversity of photoreceptors has evolved among invertebrates : 1. A diversity of photoreceptors has evolved among invertebrates Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.7 Eye cups are among the simplest photoreceptors
Detect light intensity and direction — no image formation.
The movement of a planarian is integrated with photoreception.
Slide21 : Image-forming eyes.
Compound eyes of insects and crustaceans.
Each eye consists of ommatidia, each with its own light-focusing lens.
This type of eye is very good at detecting movement. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.8
Slide22 : Single-lens eyes of invertebrates such as jellies, polychaetes, spiders, and mollusks.
The eye of an octopus works much like a camera and is similar to the vertebrate eye. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
2. Vertebrates have single-lens eyes : 2. Vertebrates have single-lens eyes Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Is structurally analogous to the invertebrate single-lens eye. Fig. 49.9
Slide24 : Sclera: a tough white layer of connective tissue that covers all of the eyeball except the cornea.
Conjunctiva: external cover of the sclera — keeps the eye moist. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide25 : Cornea: transparent covering of the front of the eye.
Allows for the passage of light into the eye and functions as a fixed lens. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide26 : Choroid: thin, pigmented layer lining the interior surface of the sclera.
Prevents light rays from scattering and distorting the image.
Anteriorly it forms the iris.
The iris regulates the size of the pupil. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide27 : Retina: lines the interior surface of the choroid.
Contains photoreceptors.
Except at the optic disk (where the optic nerve attaches). Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide28 : The lens and ciliary body divide the eye into two cavities.
The anterior cavity is filled with aqueous humor produced by the ciliary body.
Glaucoma results when the duct that drain aqueous humor are blocked.
The posterior cavity is filled with vitreous humor.
The lens, the aqueous humor, and the vitreous humor all play a role in focusing light onto the retina. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide29 : Accommodation is the focusing of light in the retina.
In squid, octopuses, and many fish this is accomplished by moving the lens forward and backward. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide30 : In mammals accommodation is accomplished by changing the shape of the lens.
The lens is flattened for focusing on distant objects.
The lens is rounded for focusing on near objects. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.10
Slide31 : Photoreceptors of the retina.
About 125 million rod cells.
Rod cells are light sensitive but do not distinguish colors.
About 6 million cone cells.
Not as light sensitive as rods but provide color vision.
Most highly concentrated on the fovea – an area of the retina that lacks rods. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
3. The light-absorbing pigment rhodopsin triggers a signal-transduction pathway : 3. The light-absorbing pigment rhodopsin triggers a signal-transduction pathway Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Rhodopsin (retinal + opsin) is the visual pigment of rods.
The absorption of light by rhodopsin initiates a signal-transduction pathway. Fig. 49.13
Slide33 : Color reception is more complex than the rhodopsin mechanism.
There are three subclasses of cone cells each with its own type of photopsin.
Color perception is based on the brain’s analysis of the relative responses of each type of cone.
In humans, colorblindness is due to a deficiency, or absence, of one or more photopsins.
Inherited as an X-linked trait. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
4. The retina assists the cerebral cortex in processing visual information : 4. The retina assists the cerebral cortex in processing visual information Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Visual processing begins with rods and cones synapsing with bipolar cells.
Bipolar cells synapse with ganglion cells.
Visual processing in the retina also involves horizontal cells and amacrine cells.
Slide35 : Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.15
Slide36 : Vertical pathway: photoreceptors bipolar cells ganglion cells axons. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide37 : Lateral pathways:
Photoreceptors horizontal cells other photoreceptors.
Results in lateral inhibition.
More distance photoreceptors and bipolar cells are inhibited sharpens edges and enhances contrast in the image.
Photoreceptors bipolar cells amacrine cells ganglion cells.
Also results in lateral inhibition, this time of the ganglion cells. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide38 : Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings The optic nerves of the two eyes meet at the optic chiasm.
Where the nasal half of each tract crosses to the opposite side.
Ganglion cell axons make up the optic tract.
Most synapse in the lateral geniculate nuclei of the thalamus.
Neurons then convey information to the primary visual cortex of the optic lobe. Fig. 49.16
Slide39 : CHAPTER 49 SENSORY AND MOTOR SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section D: Hearing And Equilibrium 1. The mammalian hearing organ is within the ear
2. The inner ear also contains the organs of equilibrium
3. A lateral line system and inner ear detect pressure waves in most fishes and aquatic amphibians
4. Many invertebrates have gravity sensors and are sound-sensitive
1. The mammalian hearing organ is within the ear : The outer ear includes the external pinna and the auditory canal.
Collects sound waves and channels them to the tympanic membrane. 1. The mammalian hearing organ is within the ear Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide41 : Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.17
Slide42 : From the tympanic membrane sound waves are transmitted through the middle ear.
Malleus incus stapes.
From the stapes the sound wave is transmitted to the oval window and on to the inner ear.
Eustachian tube connects the middle ear with the pharynx. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide43 : The inner ear consists of a labyrinth of channels housed within the temporal bone.
The cochlea is the part of the inner ear concerned with hearing.
Structurally it consists of the upper vestibular canal and the lower tympanic canal, which are separated by the cochlear duct.
The vestibular and tympanic canals are filled with perilymph. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide44 : The cochlear duct is filled with endolymph.
The organ of Corti rests on the basilar membrane.
The tectorial membrane rests atop the hair cells of the organ of Corti. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide45 : From inner ear structure to a sensory impulse: follow the vibrations.
The round window functions to dissipate the vibrations.
Vibrations in the cochlear fluid basilar membrane vibrates hair cells brush against the tectorial membrane generation of an action potential in a sensory neuron. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide46 : Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.18
Slide47 : Pitch is based on the location of the hair cells that depolarize.
Volume is determined by the amplitude of the sound wave. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
2. The inner ear also contains the organs of equilibrium : Behind the oval window is a vestibule that contains the utricle and saccule.
The utricle opens into three semicircular canals. 2. The inner ear also contains the organs of equilibrium Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide49 : Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.19
Slide50 : The utricle and saccule respond to changes in head position relative to gravity and movement in one direction.
Hair cells are projected into a gelatinous material containing otoliths.
When the head’s orientation changes the hair cells are tugged on nerve impulse along a sensory neuron. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide51 : The semicircular canals respond to rotational movements of the head.
The mechanism is similar to that associated with the utricle and saccule. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
3. A lateral line system and inner ear detect pressure waves in most fishes and aquatic amphibians : Fishes and amphibians lack cochleae, eardrums, and openings to the outside.
However, they have saccules, utricles, and semicircular canals. 3. A lateral line system and inner ear detect pressure waves in most fishes and aquatic amphibians Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide53 : Most fish and amphibians have a lateral line system along both sides of their body.
Contains mechanoreceptors that function similarly to mammalian inner ear.
Provides a fish with information concerning its movement through water or the direction and velocity of water flowing over its body. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.20
4. Many invertebrates have gravity sensors and are sound-sensitive : Statocysts are mechanoreceptors that function in an invertebrates sense of equilibrium.
Statocysts function is similar to that of the mammalian utricle and saccule. 4. Many invertebrates have gravity sensors and are sound-sensitive Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.21
Slide55 : Sound sensitivity in insects depends on body hairs that vibrate in response to sound waves.
Different hairs respond to different frequencies.
Many insects have a tympanic membrane stretched over a hollow chamber. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.22
Slide56 : CHAPTER 49 SENSORY AND MOTOR SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section E: Chemoreception – Taste And Smell 1. Perceptions of taste and smell are usually interrelated
1. Perceptions of taste and smell are usually interrelated : Taste receptors in insects are located on their feet. 1. Perceptions of taste and smell are usually interrelated Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.23
Slide58 : In mammals, taste receptors are located in taste buds most of which are on the surface of the tongue.
Each taste receptor responds to a wide array of chemicals.
It is the pattern of taste receptor response that determines something’s perceived flavor. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide59 : In mammals, olfactory receptors line the upper portion of the nasal cavity.
The binding of odor molecules to olfactory receptors initiate signal transduction pathways involving a G-protein-signaling pathway and, often, adenylyl cyclase and cyclic AMP. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.24
Slide60 : CHAPTER 49 SENSORY AND MOTOR SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section F1: Movement And Locomotion 1. Locomotion requires energy to overcome friction and gravity
2. Skeletons support and protect the animal body and are essential to movement
3. Physical support on land depends on adaptations of body proportions and posture
4. Muscles move skeletal parts by contracting
5. Interactions between myosin and actin generate force during muscle contractions
Slide61 : Locomotion is active movement from one place to another. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
1. Locomotion requires energy to overcome friction and gravity : A comparison of the energy costs of various modes of locomotion. 1. Locomotion requires energy to overcome friction and gravity Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.25
Slide63 : Swimming.
Since water is buoyant gravity is less of a problem when swimming than for other modes of locomotion.
However, since water is dense, friction is more of a problem.
Fast swimmers have fusiform bodies. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide64 : For locomotion on land powerful muscles and skeletal support are more important than a streamlined shape.
When hopping the tendons in kangaroos legs store and release energy like a spring that is compressed and released – the tail helps in the maintenance of balance.
When walking having one food on the ground helps in the maintenance of balance.
When running momentum helps in the maintenance of balance.
Crawling requires a considerable expenditure of energy to overcome friction – but maintaining balance is not a problem. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide65 : Gravity poses a major problem when flying.
The key to flight is the aerodynamic structure of wings. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 34.26
Slide66 : Cellular and Skeletal Underpinning of Locomotion.
On a cellular level all movement is based on contraction.
Either the contraction of microtubules or the contraction of microfilaments. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
2. Skeletons support and protect the animal body and are essential to movement : Hydrostatic skeleton: consists of fluid held under pressure in a closed body compartment.
Form and movement is controlled by changing the shape of this compartment.
The hydrostatic skeleton of earthworms allow them to move by peristalsis.
Advantageous in aquatic environments and can support crawling and burrowing.
Do not allow for running or walking. 2. Skeletons support and protect the animal body and are essential to movement Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide68 : Exoskeletons: hard encasements deposited on the surface of an animal.
Mollusks are enclosed in a calcareous exoskeleton.
The jointed exoskeleton of arthropods is composed of a cuticle.
Regions of the cuticle can vary in hardness and degree of flexibility.
About 30 – 50% of the cuticle consists of chitin.
Muscles are attached to the interior surface of the cuticle.
This type of exoskeleton must be molted to allow for growth. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide69 : Endoskeletons: consist of hard supporting elements within soft tissues.
Sponges have spicules.
Echinoderms have plates composed of magnesium carbonate and calcium carbonate.
Chordate endoskeletons are composed of cartilage and bone.
The bones of the mammalian skeleton are connected at joints by ligaments. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide70 : Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.28
3. Physical support on land depends on adaptations of body proportions and posture : In the support of body weight posture is more important than body proportions. 3. Physical support on land depends on adaptations of body proportions and posture Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
4. Muscles move skeletal parts by contracting : Muscles come in antagonistic pairs. 4. Muscles move skeletal parts by contracting Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.30
Slide73 : Structure and Function of Vertebrate Skeletal Muscle.
The sarcomere is the functional unit of muscle contraction.
Thin filaments consist of two strands of actin and one tropomyosin coiled about each other.
Thick filaments consist of myosin molecules. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.31
5. Interactions between myosin and actin generate force during muscle contractions : The sliding-filament model of muscle contraction. 5. Interactions between myosin and actin generate force during muscle contractions Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.33
Slide75 : CHAPTER 49 SENSORY AND MOTOR SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section F2: Movement And Locomotion (continued) 5. Interactions between myosin and actin generate force during muscle contractions
6. Calcium ions and regulatory proteins control muscle contraction
7. Diverse body movements require variation in muscle activity
5. Interactions between myosin and actin generate force during muscle contractions : The sliding-filament model of muscle contraction. 5. Interactions between myosin and actin generate force during muscle contractions Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.33
6. Calcium ions and regulatory proteins control muscle contraction : At rest tropomyosin blocks the myosin binding sites on actin.
When calcium binds to the troponin complex a conformational change results in the movement of the tropomyosin- tropinin complex and exposure of actin’s myosin binding sites. 6. Calcium ions and regulatory proteins control muscle contraction Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.34
Slide78 : But, wherefore the calcium ions?
Follow the action potential.
When an action potential meets the muscle cell’s sarcoplasmic reticulum (SR) stored Ca2+ is released. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.35
Slide79 : Review of skeletal muscle contraction. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.36
7. Diverse body movements require variation in muscle activity : An individual muscle cell either contracts completely or not all.
Individual muscles, composed of many individual muscle fibers, can contract to varying degrees.
One way variation is accomplished by varying the frequency of action potentials reach the muscle from a single motor neuron. 7. Diverse body movements require variation in muscle activity Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.37
Slide81 : Graded muscle contraction can also be controlled by regulating the number of motor units involved in the contraction. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 49.38
Slide82 : Recruitment of motor neurons increases the number of muscle cells involved in a contraction.
Some muscles, such as those involved in posture, are always at least partially contracted.
Fatigue is avoided by rotating among motor units. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide83 : Fast and Slow Muscle Fibers.
Fast muscle fibers are adapted for rapid, powerful contractions.
Fatigue relatively quickly. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide84 : Slow muscle fibers are adapted for sustained contraction.
Relative to fast fibers, slow fibers have.
Less SR Ca2+ remains in the cytosol longer.
More mitochondria, a better blood supply, and myoglobin. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide85 : Other Types of Muscle.
In addition to skeletal muscle, vertebrates have cardiac and smooth muscle.
Cardiac muscle: similar to skeletal muscle.
Intercalated discs facilitate the coordinated contraction of cardiac muscle cells.
Can generate there own action potentials.
Action potentials of long duration. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide86 : Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 40.4
Slide87 : Smooth muscle: lacks the striations seen in both skeletal and cardiac muscle.
Contracts with less tension, but over a greater range of lengths, than skeletal muscle.
No T tubules and no SR.
• Ca2+ enters the cytosol from via the plasma membrane.
Slow contractions, with more control over contraction strength than with skeletal muscle.
Found lining the walls of hollow organs. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Slide88 : Invertebrate muscle cells are similar to vertebrate skeletal and smooth muscle cells. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings