Podcast
Questions and Answers
What is the structural unit of the nervous system?
What is the structural unit of the nervous system?
Which part of the nervous system is responsible for involuntary movements?
Which part of the nervous system is responsible for involuntary movements?
What type of stimulus has an intensity greater than the threshold?
What type of stimulus has an intensity greater than the threshold?
Which structure is NOT part of the central nervous system?
Which structure is NOT part of the central nervous system?
Signup and view all the answers
What is the term for the electrical changes that occur as a response to stimuli in nerves?
What is the term for the electrical changes that occur as a response to stimuli in nerves?
Signup and view all the answers
Which of the following is NOT classified under the sensory part of the nervous system?
Which of the following is NOT classified under the sensory part of the nervous system?
Signup and view all the answers
What type of stimulus is a sudden change in the environment?
What type of stimulus is a sudden change in the environment?
Signup and view all the answers
Which division of the nervous system is primarily involved in transmitting sensations from receptors to sensory centers?
Which division of the nervous system is primarily involved in transmitting sensations from receptors to sensory centers?
Signup and view all the answers
Which type of conduction occurs in myelinated nerve fibers?
Which type of conduction occurs in myelinated nerve fibers?
Signup and view all the answers
What does the all or none law state regarding nerve responses?
What does the all or none law state regarding nerve responses?
Signup and view all the answers
Which of the following is NOT an example of the all or none law?
Which of the following is NOT an example of the all or none law?
Signup and view all the answers
What is the local excitatory state produced by subthreshold stimuli?
What is the local excitatory state produced by subthreshold stimuli?
Signup and view all the answers
What is the consequence of strong stimulus application during the subnormal phase?
What is the consequence of strong stimulus application during the subnormal phase?
Signup and view all the answers
Which ion's release triggers the binding of myosin heads to actin in skeletal muscle contraction?
Which ion's release triggers the binding of myosin heads to actin in skeletal muscle contraction?
Signup and view all the answers
What initiates the process of excitation-contraction coupling in muscle fibers?
What initiates the process of excitation-contraction coupling in muscle fibers?
Signup and view all the answers
What is the role of ATP and creatine phosphate during nerve impulse propagation?
What is the role of ATP and creatine phosphate during nerve impulse propagation?
Signup and view all the answers
Study Notes
Nervous System - Excitable Tissues
- The neuron is the structural unit of the nervous system.
- Reflex action is the functional unit, involving receptor, afferent, center, efferent, and effector organs.
-
Anatomical Classification:
- CNS (Central Nervous System) includes the brain (cerebrum, subcortical centers, cerebellum, brain stem) and spinal cord (31 segments with horns and columns).
- PNS (Peripheral Nervous System) includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.
-
Physiological Classification:
- Sensory part transmits sensations from receptors to sensory centers (e.g., somatic, visceral, special senses).
- Motor part transmits orders from motor centers to effector organs (somatic and autonomic).
Nerve Properties
-
Excitability:
- Nerves respond to stimuli (electrical, chemical, mechanical, thermal).
- Threshold stimulus is the minimum intensity needed for a response.
- Subthreshold stimuli have intensities less than the threshold.
- Suprathreshold stimuli have intensities greater than the threshold.
- Responses involve electrical changes (action potentials), excitability changes, metabolic changes, and thermal changes.
-
Conductivity:
- Nerve impulses are conducted along nerve fibers.
- Unmyelinated fibers conduct impulses via sweeping conduction.
- Myelinated fibers conduct impulses via saltatory conduction.
All or None Law
- Nerve fibers either respond maximally or not at all to a threshold stimulus, provided other factors affecting excitability remain constant.
- Applies to: single nerve fiber, single motor unit, cardiac muscle, and unitary smooth muscle.
- Does not apply to: whole skeletal muscle, nerve trunks, and multiunit smooth muscle.
Summation
- Subthreshold stimuli, applied successively within short periods (<0.5 ms), can summate to produce an action potential.
Adaptation (Accommodation)
- Nerve fibers quickly adapt to constant or gradually increasing stimuli.
- The response to a constant stimulus is only at the beginning and end; no response occurs during the actual stimulus.
Infatigability
- Nerve fibers don't become fatigued with repeated stimulation.
Electrical Changes in Nerves
- Resting Membrane Potential (RMP): The potential difference between the outer and inner surfaces of a nerve cell membrane at rest. Typically around -70mV.
- Selective permeability and Na+/K+ pump are crucial for maintaining RMP. The Na+/K+ pump pumps 3 sodium ions out and 2 potassium ions in for each ATP.
- Depolarization: A reduction in the membrane potential (e.g. moving toward 0 mV).
- Repolarization: A return to the resting membrane potential.
- Hyperpolarization: An increase in the membrane potential (e.g. moving further from 0 mV).
- Action Potential: The sequence of depolarization and repolarization that occurs in response to a stimulus strong enough to reach the threshold potential.
Mechanism of Neurotransmission
- Nerve impulse transmission occurs at the neuromuscular junction.
- This involves the release of acetylcholine, which triggers depolarization in the muscle.
Mechanism of Skeletal Muscle Contraction
- Depolarization of the muscle fiber initiates contraction.
- Release of Ca2+ from the sarcoplasmic reticulum allows binding of myosin heads to actin, leading to a sliding filament mechanism.
Propagation of Nerve Impulse
- Absolute Refractory Period: During this period, the nerve cannot respond to further stimuli. Coincides with ascending limb of action potential).
- Relative Refractory Period: The nerve can respond to stimulation but a stronger stimulus is required. Coincides with remaining part of repolarization).
- Supernormal Phase: Excitability is higher than normal.
- Subnormal Phase: Excitability is lower than normal.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the complexities of the nervous system in this quiz focusing on excitable tissues. Understand the structural and functional units of neurons, classifications of the nervous system, and the properties of nerve responses. Test your knowledge on both anatomical and physiological aspects.
