Unit2

Excitable cell

A cell that uses the resting membrane potential to generate an electrochemical impulse called an action potential.

Non-excitable cell

A cell that does not generate action potentials.

Depolarization

The process by which ions move in and out of the cell making the inside more positive relative to the resting membrane potential.

Hyperpolarization

K+ leaves the cell, making the inside more negative than the resting potential.

Voltage-gated channels

Ion channels that open in response to changes in membrane voltage.

Chemically-gated channels

Ion channels that open when a specific chemical (ligand) binds.

Threshold for action potential

The level (-55 mV) that must be reached to trigger an action potential.

Resting state

The state in which the resting membrane potential has been restored after an action potential.

Absolute refractory period

The period during depolarization and repolarization when no new action potential can be initiated.

Relative refractory period

The period when the cell is more negative than the resting potential, making it harder to generate a new action potential.

Myelin Sheath

Insulating layers that form around axons, ensuring faster transmission of the action potential.

Nodes of Ranvier

Myelin-sheath gaps rich in ion channels that facilitate the fast propagation of an action potential.

Dendrites

Projections of the soma that direct action potentials towards the soma.

Axon terminals

The ends of the axon that transmit information to the next cell via neurotransmitter release.

Central Nervous System (CNS)

The part of the nervous system consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

The part of the nervous system that includes nerves extending from the CNS to muscles and organs.

Somatomotor division

Part of the PNS controlling skeletal muscles for voluntary movement.

Autonomic division

Part of the PNS controlling involuntary organs.

Bipolar neuron

A neuron with one axon and one dendrite, found in the retina of the eye.

Unipolar neuron

A neuron with a straight connection between axon and dendrite, primarily sensory in nature.

Multipolar neuron

A neuron with many branching dendrites and one axon, most common in the CNS.

Ependymal cells

Glial cells that produce cerebrospinal fluid and line the brain's ventricles and spinal cord.

Oligodendrocytes

Myelin-forming cells in the CNS that myelinate several axons.

Astrocytes

Most abundant glial cells that provide physical and nutritional support to neurons.

Microglia

Immune cells in the CNS that engulf and remove foreign materials or damaged cells.

Schwann cells

Glial cells of the PNS that produce myelin and promote regeneration of peripheral nerves.

Multiple Sclerosis (MS)

An autoimmune disease that attacks the myelin sheaths of neurons.

Gyri

The bumps on the brain's surface.

Sulci

The dips or valleys between gyri on the brain.

Cerebellum

The part of the brain responsible for coordinated movement and balance.

Thalamus

The brain structure that relays sensory information to the cortex.

Hypothalamus

Regulates homeostasis and controls various endocrine functions.

Neurotransmitters

Chemicals that neurons release to communicate with each other.

Synapse

The junction where neurons exchange information.

Electrical synapse

A synapse where neurons directly exchange ions through gap junctions.

Chemical synapse

A synapse where neurons release neurotransmitters across a synaptic cleft.

Graded potentials

Small changes in membrane potential that do not trigger an action potential on their own.

EPSP

Excitatory post-synaptic potential, which brings the neuron closer to an action potential.

IPSP

Inhibitory post-synaptic potential, which pushes the neuron further away from triggering an action potential.

Integration of EPSP and IPSP

The process where a post-synaptic neuron receives inputs from multiple pre-synaptic neurons.

Muscle fibers

Cells that make up the skeletal muscle, also known as muscle cells.

Triad structure

A structure in skeletal muscle fibers consisting of one T-tubule and two terminal cisternae.

Myofibrils

Bundles of myofilaments that run parallel to each other within skeletal muscle fibers.

Sarcomeres

The contractile units of muscle fibers composed of thick and thin filaments.

Actin

Thin myofilaments that are involved in muscle contraction.

Myosin

Thick myofilaments that pull on actin during muscle contraction.

Excitation-contraction coupling

The process that links muscle excitation to muscle contraction.

Power stroke

The action of myosin heads pulling actin filaments towards the center of the sarcomere during contraction.

Rigor mortis

A post-death condition where muscles become stiff due to permanent actin-myosin cross-links.

Motor unit

A motor neuron and all the muscle fibers it innervates.

Twitch

A single contraction of a muscle in response to one action potential.

Latent period

The time delay between action potential and measurable muscle tension during a muscle twitch.

Summation of twitches

Increased tension from multiple action potentials occurring close together.

Unfused tetanus

A state where twitches partially overlap but allow some relaxation.

Complete tetanus

A sustained contraction with no relaxation between twitches due to high frequency of action potentials.

Corticospinal tract

The motor pathway that controls voluntary movements.

Proprioception

The awareness of body position and movement in space.

Stretch reflex

A reflex arc where stretching of a muscle causes it to contract automatically.

Cerebellum's role in movement

To correct ongoing movements by comparing intended and actual movements.

Hypothalamus functions

Regulates homeostasis and coordinates autonomic responses.

Sympathetic division of ANS

Activates 'fight or flight' responses, increasing heart rate and energy mobilization.

Parasympathetic division of ANS

Promotes 'rest and digest' functions, slowing heart rate and increasing digestive activity.

Enteric nervous system

A division of the autonomic nervous system that controls gut motility and function.

Adrenergic receptors

Receptors that respond to norepinephrine and epinephrine, mediating sympathetic effects.

Muscarinic receptors

Receptors for acetylcholine that mediate parasympathetic effects.

Nicotinic receptors

Receptors that respond quickly to acetylcholine at autonomic ganglia and NMJ.

Negative feedback loop

A process in homeostasis where a change triggers a response that counteracts the initial change.

Functional organization of the ANS

The division of the autonomic nervous system into sympathetic, parasympathetic, and enteric divisions.

Neural plasticity

The ability of the brain and nervous system to change and adapt as a result of experience.

Directional terms in anatomy

Terms used to describe locations or positions of structures in the body.

Somatic reflexes

Reflex actions involving the contraction of skeletal muscles.

Autonomic reflexes

Reflex actions involving the autonomic nervous system and smooth muscles or glands.

Basal ganglia

A group of nuclei in the brain involved in motor control and coordination.

Homunculus

A representation of the body in the brain, illustrating how different body parts are controlled.

Mirror box therapy

A rehabilitation technique for promoting movement and reducing pain, especially after amputation.

Vestibular ocular reflex (VOR)

A reflex that stabilizes vision by coordinating eye and head movements.

Pituitary gland

A gland that regulates endocrine organs, acting under the influence of the hypothalamus.

Action potential propagation

The process by which action potentials travel along the axon.

Integration of motor control

The coordination of muscle movements through brain pathways and feedback.

Calcium's role in muscle contraction

Calcium ions released from the sarcoplasmic reticulum bind to troponin, leading to muscle contraction.

Muscle fatigue

The decline in ability of a muscle to generate force, often due to depletion of energy sources.

Reflex arc components

Sensory receptor, sensory neuron, integration center, motor neuron, effector.

Alpha motor neurons

Neurons that innervate extrafusal fibers and are responsible for muscle contraction.

Gamma motor neurons

Neurons that innervate intrafusal fibers, maintaining the sensitivity of muscle spindles.

Neuromuscular junction (NMJ)

The synapse between a motor neuron and a skeletal muscle fiber.

ACh and NMJ function

Acetylcholine binds to receptors on muscle fibers triggering contraction.

Stretch reflex pathway

Muscle spindle → sensory neuron → spinal cord → motor neuron → muscle.

Reciprocal inhibition

The process that ensures one muscle relaxes while its antagonist contracts.

Spinal reflexes

Reflex actions mediated by the spinal cord without direct involvement of the brain.

Reflexive motor responses

Automatic responses to stimuli that do not require conscious thought.

Visceral reflexes

Reflexes involving internal organs, controlled by the autonomic nervous system.

Neurotransmitter release mechanism

The process by which neurotransmitters are released from the presynaptic neuron in response to an action potential.

Cerebellar function in movement

Adjusts motor commands based on feedback from proprioceptors.

Spinal pathways for motor control

Connect the brain to the muscles and control voluntary movement.

Homeostatic control systems

Systems that maintain stable internal conditions in the body.

Central pattern generators

Neuronal circuits that produce rhythmic motor patterns like walking.

Cognitive aspects of movement

The mental processes involved in planning and executing movements.

Neuronal plasticity in recovery

The ability of the nervous system to reorganize and adapt following injury.

Chemical synapse components

Presynaptic neuron, synaptic cleft, postsynaptic neuron, and neurotransmitters.

Neuroplasticity and learning

The capacity of synapses and neural networks to change in response to experience.