Nerves and muscles

1. NERVE AND MUSCLE
PHYSIOLOGY
BMS 232

2. LEARNING OBJECTIVES
1.1 Explain in simple terms the levels of organization of nervous
system
1.2 Recall the physiological functioning of neurons, neuroglia
cells, nerve and muscle cells
1.3 Define different physiological concepts, control mechanisms,
various receptors and life processes in relation to the nerves and
muscles.

3. INTRODUCTION
• The nervous system is the master controlling & communicating
system of the body
• Every thought, action & emotion reflects its activity
• Its cells communicate by signals, which are rapid & specific, &
usually causes immediate responses

4. NERVOUS SYSTEM
1. It monitors the changes occurring inside & outside the body………This
gathered information is called (Sensory input)
2. It interprets this sensory input & decides what should be done at each
moment …………… (Integration)
3. It causes a response……………(Motor output) (By activating effector organs)

5. Example
When you are driving, & see a red light ……… Sensory input
Your nervous system integrates this information (Red means stop)
……….. Integration
Your foot will go to the break ……….. Motor output
NERVOUS SYSTEM

6. Central nervous system Peripheral nervous system
(CNS) (PNS)
Brain Cranial nerves
Spinal cord Spinal nerves
NERVOUS SYSTEM

8. • Basic structural and functional units of the nervous
system.
• Cannot divide by mitosis.
• Respond to physical and chemical stimuli.
• Produce and conduct electrochemical impulses.
• Release chemical regulators.
• Nerve:
• Bundle of axons located outside CNS.
• Most composed of both motor and sensory fibers.
NEURON

10. Based upon direction impulses
conducted.
Sensory
Transmit impulses from organs to CNS
Motor
Transmit impulses away from CNS to
the effector organs (Muscles, glands)
Interneurons
Located entirely within the CNS.
Serve an integrative function.
FUNCTIONAL CLASSIFICATION OF NEURONS

11. •Neurons are highly irritable (responsive to stimuli)
•When a neuron is stimulated, an impulse is
generated & conducted along the neuron …….. This
response is called (Action potential)
ACTION POTENTIAL

12. • Leakage channels
• Gated channels open and close in response to a stimulus
results in neuron excitability
• voltage-gated open in response to change in voltage
• ligand-gated open & close in response to particular
chemical stimuli (hormone, neurotransmitter, ion)
• mechanically-gated open with mechanical stimulation
ACTION POTENTIAL

13. When these ion channels open, ions diffuse quickly across the
membrane from area of high concentration to area of low
concentration
Resting membrane potential
Inside the membrane is more negative than outside
(This state is called Resting membrane potential)
The resting membrane potential of large nerve fibers
when not transmitting nerve signals is about –90
millivolts.
ACTION POTENTIAL

14. Factors that determine the level of resting potential
are:
1-Active Transport of Sodium and Potassium Ions Through the
Membrane—The Sodium- Potassium (Na+-K+) Pump
2-Leakage of Potassium and Sodium Through the Nerve Membrane.
ACTION POTENTIAL

15. 1. Resting state:
Na+ & K+ channels are closed
2. Depolarization:
Na+ channels open & K+ channels still closed
& so……Na+ ions will rush inside the cell ……. Leading to more +ve
charge inside
3. Repolarization:
Na+ entry will decline …… K+ channels will open & K+ rush out of the cell
…… & so negativity inside the membrane will be restored
STEPS OF ACTION POTENTIAL

16. 4. Na+ K+ pump
The ion redistribution will be accomplished by Sodium-
Potassium pump (Will take K+ ions inside & Na+ ions outside)
This action potential will be propagated along the entire axon
STEPS OF ACTION POTENTIAL

18. STEPS OF ACTION POTENTIAL

19. https://www.youtube.com/watch?v=iBDXOt_uHTQ

20. • When the impulse reaches the axon terminal, it sets
certain events that lead to neurotransmitter release.
• The neurotransmitter crosses the synaptic cleft & binds
to receptors on the postsynaptic membrane …… Leading
to transfer of impulse
NERVE IMPULSE TRANSMISSION

21. •Functional connection between a neuron and
another neuron or effector cell.
•Transmission in one direction only.
•Synaptic transmission is through a chemical
gated channel.
SYNAPSE

22. SYNAPSE
Electrical Synapse
• Impulses can be regenerated
without interruption in
adjacent cells.
Examples:
• Smooth and cardiac
muscles, brain, and glial
cells.

23. SYNAPSE
•Chemical Synapse
• Terminal bouton is
separated from
postsynaptic cell by
synaptic cleft.

24. SYNAPTIC TRANSMISSION
1. Opening Ca2+ channels in the presynaptic axon
terminal
When the impulse reaches the axon terminal, Ca2+ channels will
open …….. & Ca2+ will pass inside the membrane
2. Neurotransmitter is released
The Ca2+ entrance causes the synaptic vesicles to fuse with the
membrane, & empty their contents into the synaptic cleft

25. 3. Neurotransmitter binds to postsynaptic receptors
The neurotransmitter that diffuses across the synaptic cleft binds
reversibly to specific receptor on the postsynaptic membrane
4. Ion channels open in the postsynaptic membrane
When the neurotransmitter binds to the receptor, this will cause ion
channels to open & creates an action potential
5. Neurotransmitter effects are terminated
After that the effect of the neurotransmitter will be terminated by one
of the following methods
SYNAPTIC TRANSMISSION

26. 1. Degradation by enzymes
(As: acetylcholine …..degraded by enzyme called:
Acetylcholine esterase)
2. Reuptake by the presynaptic terminal
(As: norepinephrine)
3. Diffusion away from the synapse
FATE OF NERVE IMPLUSE

27. MUSCLES
Three basic muscle types are found in the body
Skeletal muscle
Cardiac muscle
Smooth muscle

28. CONNECTIVE TISSUE WRAPPINGS OF
SKELETAL MUSCLE
Endomysium – around single muscle
fiber
Perimysium – around a fascicle
(bundle) of fibers
Epimysium – covers the entire
skeletal muscle
Fascia – on the outside of the
epimysium

29. MICROSCOPIC ANATOMY OF SKELETAL
MUSCLE
• Cells are multinucleate
• Nuclei are just beneath the sarcolemma

30. MICROSCOPIC ANATOMY OF SKELETAL
MUSCLE
•Myofibril
•Bundles of myofilaments
•Myofibrils are aligned to give distinct bands
•I band = light band
•A band = dark band

31. Sarcomere
Contractile unit of a muscle fiber
MICROSCOPIC ANATOMY OF SKELETAL
MUSCLE

32. MICROSCOPIC ANATOMY OF SKELETAL
MUSCLE
Organization of the sarcomere
Thin filaments = actin filaments
Composed of the protein actin

33. PROPERTIES OF SKELETAL MUSCLE ACTIVITY
(SINGLE CELLS OR FIBERS)
Irritability – ability to receive and respond to a
stimulus
Contractility – ability to shorten when an adequate
stimulus is received

34. NERVE STIMULUS TO MUSCLES
Skeletal muscles must be stimulated by
a nerve to contract (motor neuron)
Motor unit
One neuron
Muscle cells stimulated by that neuron

35. NERVE STIMULUS TO MUSCLES
•Neuromuscular junctions – association site
of nerve and muscle

36. NERVE STIMULUS TO MUSCLES
Synaptic cleft – gap between nerve and muscle
Nerve and muscle do not make contact
Area between nerve and muscle is filled with
interstitial fluid

37. TRANSMISSION OF NERVE IMPULSE TO
MUSCLE
Neurotransmitter – chemical released by nerve
upon arrival of nerve impulse
The neurotransmitter for skeletal muscle is acetylcholine
Neurotransmitter attaches to receptors on the
sarcolemma
Sarcolemma becomes permeable to sodium (Na+)

38. REFERENCES
1. STUART IRA FOX 14TH EDITION (CHAPTER 12)
2. HUMAN ANATOMY AND PHYSIOLOGY BY ELAINE N MARIEB KATJA
HOEHN 10th EDITION (unit 3 chapter 11)

39. Thank you