Excitable tissue: Muscle Physiology Flashcards
(23 cards)
Differentiate between the different layers of connective tissue in and around a muscle.
Endomysium: envelops a muscle fibre
Perimysium: envelops a bundle of muscle fibres
Epimysium: envelops a muscle
What contributes to the striated appearance of skeletal muscle?
myofibrils contain units called sarcomeres that are composed of actin (thin filaments) and myosin (thick filaments), which create alternating light (I bands) and dark (A bands) regions when viewed under a microscope.
What is a sarcomere?
The structural/ functional/ contractile units of skeletal muscle fibres.
What is the difference between isometric and isotonic muscle contraction?
Isometric Contraction (Static)
- The muscle contracts without changing length.
- No movement occurs, but tension is generated.
Example: Holding a plank position or gripping an object without moving.
Isotonic Contraction (Dynamic)
- The muscle changes length while contracting.
- Movement occurs, and tension remains relatively constant.
Two types:
- Concentric contraction – Muscle shortens (e.g., lifting a dumbbell).
- Eccentric contraction – Muscle lengthens under tension (e.g., lowering a dumbbell).
Differentiate between nuclei and ganglia
Collection of nerve cell bodies in:
CNS = nuclei
PNS = ganglia
T/F: Interneurons are only found in the CNS
True
Differentiate between graded potentials and action potentials
Graded potentials:
- amplitude depends on stimulus strength
- hyper (IPSP) /depolarising (EPSP)
- Occur in dendrites/ nerve cell body
- Multiple GP can summate into an AP
- no refractory period
Action potentials:
- Occur once threshold is reached
- depolarising
- occurs in axon
- has a refractory period
Graded potentials initiate an action potential if they reach the threshold.
Differentiate between a neuromuscular junction and a neuroeffector junction
Neuromuscular Junction:
- Connects a motor neuron to a skeletal muscle fiber.
- NT = acetylcholine (ACh)
- ACh binds to nicotinic receptors on the muscle = contraction
- voluntary movement.
Neuroeffector Junction:
- Connects a motor neuron to a non-muscular target cell (e.g., smooth muscle, cardiac muscle, or glands).
- Various NT’s (e.g., norepinephrine, acetylcholine)
- excitatory/ inhibitory
- Autonomic nervous system functions (e.g., digestion, heart rate regulation).
Differentiate between temporal and spatial summation
Temporal Summation:
- Multiple signals from the same presynaptic neuron occur in rapid succession.
= If the interval between signals is short, the effects add up, increasing depolarization.
= Helps a single weak stimulus become strong enough to trigger an action potential.
Spatial Summation:
- Multiple signals from different presynaptic neurons occur at the same time.
= If enough excitatory inputs arrive simultaneously, they combine to reach the threshold.
= Can involve both excitatory (EPSPs) and inhibitory (IPSPs) inputs, which compete to determine the final effect.
Both types of summation occur at the axon hillock
What is the difference between agonists and antagonists?
Agonist: Mimics natural ligands by binding to their receptors and initiating the same biological response
Antagonist: Blocks receptors by binding to them to prevent activation by natural ligands/ agonists, produces no biological response.
What is resting membrane potential?
Voltage/ charge/ potential difference across the cell membrane i.e. between the interior and exterior of a cell of a cell at rest (not actively sending signals)
What 5 structures make up the basal ganglia/ nuclei?
1) Caudate nuclei
2) Putamen
1 + 2 forms the Striatum
3) Globus Pallidus
4) Subthalamic nucleus
5) Substantia nigra
What structures are included in the limbic system?
Cingulate gyrus (cerebral cortex)
Hypothalamus
Hippocampus
Amygdala
What is the function of the thalamus?
Relay station for all sensory pathways except olfactory.
Relays info from the cerebellum and basal ganglia to cerebral cortex (motor cortex) to control muscle coordination.
What structures make up the brain stem?
Midbrain, medulla oblongata, pons
What structures make up the midbrain (mesencephalon)?
1) Tectum (roof)
Mammals:
- Superior colliculi = visual reflexes
- Inferior colliculi = auditory reflexes
Birds: Tectum = visual processing
2)Tegmentum:
- Red nucleus: motor movement (voluntary)
- Substantia nigra: part of basal nuclei - produces dopamine (hypothalamus does too)
3) Cerebral peduncles:
Contain ascending and descending nerve tracts.
What is the lumbar cistern?
A sac formed by the extension of dura, arachnoid and subarachnoid beyond where the spinal cord terminates, filled with CSF. Used to sample CSF.
Briefly describe the divisions of the nervous system
The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
CNS = Brain + spinal cord
PNS
= Sensory (afferent division)
+
= Motor (efferent) division
- Somatic NS (voluntary - skeletal m.)
- Autonomic NS (involuntary - smooth
+ cardiac m. + glands)
> Sympathetic
> Parasympathetic
What information is carried via the spinothalamic tract pathway and how does this pathway work?
pain/ temp. stimulus > nociceptor (pain)/ thermoreceptor (temp.) > 1st. (afferent, sensory) neuron > SC > 2nd neuron in grey matter of SC > crosses over (decussates) > ascends to thalamus > 3rd neuron in thalamus > somatosensory cortex (cerebral cortex > parietal lobe)
What are axon collaterals?
Side branches extending from the axon of a neuron at right (90 degree) angles.
What information is carried via the dorsal column pathway and how does this pathway work?
body movement, limb position (proprioception), touch and pressure, vibration = stimulus > mechanoreceptors > 1st. (afferent, sensory) neuron > SC > Ascends to brainstem > 2nd neuron in brain stem > crosses over (decussates) > thalamus > 3rd neuron > somatosensory cortex (cerebral cortex > parietal lobe)
Name 3 primary afferent neurons (nerve fibres), their characteristics and what they are stimulated by and what neurotransmitters they use
1) A-beta nerve fibres:
- touch/pressure (not pain)
mechanoreceptors (proprioceptors)
= thick, myelinated, fast conduction velocity
-NT = glutamate
2) A-delta nerve fibres:
-stinging/ pricking sensation
=medium, myelinated, medium conduction velocity
-NT = glutamate
3) C- fibres:
-dull pain, burning, aching
= thin, unmyelinated, slow conduction velocity
- NT = glutamate + substance P
A-delta and C fibres transmit noxious (harmful stimuli)
What is the Gate Control Theory of Pain Reduction?
Non-nociceptive (non-pain) receptors can influence nociceptive (pain) receptors:
