phys 2

CNS (Central Nervous System)

Consists of the brain and spinal cord.

PNS (Peripheral Nervous System)

Includes all nerves outside the CNS.

Sensory pathway

Carries signals to the CNS.

Motor pathway

Carries signals from the CNS.

Autonomic nervous system

Controls involuntary actions without conscious control.

Axon hillock

Site where action potentials start and summation of inputs occurs.

Myelin

Lipid insulation around axons that speeds up action potentials.

Schwann cells

Myelinate axons in the Peripheral Nervous System.

Oligodendrocytes

Myelinate axons in the Central Nervous System.

Microglia

Glial cells that perform phagocytosis and immune defense.

Resting membrane potential (RMP)

The membrane potential of a neuron at rest, approximately -70 mV.

Depolarization

When the membrane becomes less negative.

Repolarization

When the membrane returns to resting potential.

Hyperpolarization

When the membrane becomes more negative than -70 mV.

Ligand-gated channels

Channels that open when a neurotransmitter binds.

Mechanical-gated channels

Channels that respond to physical stimuli.

Leak channels

Channels that are always open and not gated.

Voltage-gated channels

Channels that open when the membrane potential changes.

Threshold

The membrane potential that must be reached to trigger an action potential, approximately -55 mV.

Graded Potentials

Changes in membrane potential that can be depolarizing or hyperpolarizing but do not produce action potentials directly.

Action Potentials

All-or-nothing electrical signals that propagate along neurons.

Absolute refractory period

Period during depolarization when no new action potential can occur.

Relative refractory period

Period during hyperpolarization when a stronger stimulus is required to produce an action potential.

Saltatory Conduction

The process by which action potentials jump between nodes of Ranvier in myelinated axons.

Synapse

The junction between neurons.

Excitatory neurotransmitters

Cause depolarization in the postsynaptic neuron.

Inhibitory neurotransmitters

Cause hyperpolarization in the postsynaptic neuron.

Temporal summation

Summation of rapid signals from one neuron.

Spatial summation

Summation of signals from multiple neurons.

Gyri

Bumps or folds on the surface of the brain.

Corpus callosum

Connects the left and right hemispheres of the brain.

Gray matter

Contains neuron cell bodies and is located superficially in the brain.

White matter

Composed of myelinated axons and located deeper in the brain.

Frontal lobe

Involved in decision making and contains the motor cortex.

Parietal lobe

Responsible for sensory processing, including the somatosensory cortex.

Temporal lobe

Involved in hearing.

Occipital lobe

Responsible for vision.

Broca’s area

Associated with motor speech production.

Wernicke’s area

Associated with speech comprehension.

Thalamus

Functions as a sensory relay station.

Hypothalamus

Regulates homeostasis and controls the pituitary gland.

Midbrain, Pons, and Medulla oblongata

Components of the brainstem that control vegetative functions.

Reticular Activating System (RAS)

Promotes wakefulness and alertness.

REM sleep

The sleep state associated with dreaming.

NREM sleep

Consists of stages 1-4 of sleep.

Cerebellum

Coordinates movement and balance, damage results in ataxia.

Ascending tracts

Carry sensory signals from the body to the brain.

Descending tracts

Carry motor signals from the brain to the body.

Reflex Arc

The neural pathway that controls reflex actions.

Sympathetic nervous system

Responsible for the fight or flight response.

Parasympathetic nervous system

Responsible for the rest and digest functions.

Beta blockers

Drugs that block sympathetic effects.

Albuterol

A beta agonist that opens airways.

Atropine

Blocks muscarinic receptors and causes pupil dilation.

Sensation

The detection of stimulus by sensory receptors.

Perception

The interpretation of sensory stimuli by the brain.

Taste receptors

Detect specific taste modalities such as salty, sour, sweet, bitter, and umami.

Smell (Olfaction)

The detection of odor molecules by the olfactory receptors.

Vestibular System

Responsible for balance and located in the temporal bone.

Hearing process

Involves tympanic membrane vibration and subsequent fluid movement in the cochlea.

Eye Structures

Includes cornea, lens, and iris, which are crucial for focusing light.

Photoreceptors

Cells in the retina that detect light; includes rods and cones.

Dark adaptation

Regeneration of rods pigments in low light conditions.

Light adaptation

Breakdown of cone pigments in bright light conditions.

Hypothalamus & Pituitary

Hypothalamus controls the pituitary through releasing hormones.

Anterior Pituitary Hormones

Includes FSH, LH, TSH, ACTH, Growth Hormone, and Prolactin.

Posterior Pituitary

Releases hormones made in the hypothalamus such as ADH and Oxytocin.

Adrenal Cortex

Produces steroid hormones including mineralocorticoids, glucocorticoids, androgens.

Adrenal Medulla

Releases epinephrine and norepinephrine; part of the sympathetic nervous system.

Thyroid Hormones

Includes T3 and T4, increasing metabolism and sensitivity to catecholamines.

Hypothyroidism

Condition characterized by low metabolism and possible goiter.

Hyperthyroidism

Condition known as Graves disease; may cause bulging eyes.

PTH (Parathyroid Hormone)

Increases blood calcium levels by breaking down bone.

Calcitonin

Hormone that has the opposite effect of PTH, building bone.

Pancreas

Contains alpha cells (glucagon) and beta cells (insulin) for blood glucose regulation.

Melatonin

Hormone secreted by the pineal gland that regulates sleep cycles.