Nervous System

What is a neuron?

The functional unit of the nervous system that receives and transmits signals through electrochemical signaling molecules.

What are dendrites?

Branched extensions that receive signals and transmit them to the cell body.

What is the axon hillock?

The region where action potentials are initiated.

What is the axon?

A fiber that conducts action potentials away from the cell body.

What is the myelin sheath?

A segmented covering on axons that enhances signal propagation speed via saltatory conduction at the nodes of Ranvier.

What are the glial cells of the central nervous system (CNS)?

Oligodendrocytes, microglia, ependymal cells, and astrocytes.

What are the glial cells of the peripheral nervous system (PNS)?

Schwann cells and satellite cells.

What are the types of gated ion channels?

Voltage-gated, ligand-gated, and mechanically gated.

What is the resting membrane potential of a neuron?

-70 mV (polarized).

What is the threshold potential required to trigger an action potential?

-55 mV.

What happens during depolarization of an action potential?

Voltage-gated sodium channels open, sodium rushes in, and membrane potential rises toward +30 mV.

What happens during repolarization?

Voltage-gated potassium channels open, potassium rushes out, and sodium channels inactivate, returning the membrane potential to negative.

What happens during hyperpolarization?

Potassium channels close slowly, causing the membrane potential to drop below resting levels (-80 mV).

How is the resting membrane potential restored?

By the Sodium-Potassium ATPase pump (pumping 3 sodium out and 2 potassium in per ATP).

What is the absolute refractory period?

A period during depolarization and most of repolarization when no additional action potential can be triggered.

What is the relative refractory period?

A period when an action potential can be triggered only with a stronger-than-usual stimulus overcoming hyperpolarization.

What is the difference between electrical and chemical synapses?

Electrical synapses pass ions directly through gap junctions; chemical synapses release neurotransmitters into the synaptic cleft.

What is the role of calcium ions in synaptic transmission?

An action potential opening voltage-gated calcium channels triggers the exocytosis of neurotransmitter vesicles into the synaptic cleft.

What are EPSPs and IPSPs?

Excitatory postsynaptic potentials depolarize the membrane; inhibitory postsynaptic potentials hyperpolarize the membrane.

What enzyme breaks down acetylcholine at the neuromuscular junction?

Acetylcholinesterase.

What is nitric oxide?

A gaseous neurotransmitter released on demand that relaxes smooth muscles and causes vasodilation.

What are the three meninges surrounding the CNS?

Dura mater, arachnoid mater, and pia mater.

What is cerebrospinal fluid (CSF)?

Fluid supplied by the choroid plexus/pia mater beneath the arachnoid mater that nourishes the CNS and acts as a shock absorber.

Where is gray matter versus white matter located in the brain and spinal cord?

In the brain, gray matter is outside and white matter is inside; in the spinal cord, gray matter is inside and white matter is outside.

What are the main functions of the cerebrum?

Controls voluntary muscle function, conscious thought, sensory processing, memory, learning, and communication.

What connects the two cerebral hemispheres?

Corpus callosum.

What is the function of the frontal lobe?

Contains the prefrontal cortex, motor cortex, and Broca's area.

What is the function of the parietal lobe?

Contains the somatosensory cortex, processing sensory information like touch, pressure, pain, and proprioception.

What is the function of the occipital lobe?

Contains the visual cortex, processing visual input and object recognition.

What is the function of the temporal lobe?

Contains the auditory cortex, Wernicke's area, and olfactory cortex.

What is the function of the hypothalamus?

Regulates autonomic functions, body temperature, heart rate, hunger, and monitors blood solute concentration.

What is the function of the amygdala?

Processes strong emotions like fear, anger, and pleasure.

What is the function of the hippocampus?

Essential for long-term memory formation.

What are the components of the brainstem?

Midbrain, pons, and medulla oblongata.

What is the function of the cerebellum?

Coordinates balance, posture, and fine motor control.

What is the difference between afferent and efferent nerves?

Afferent nerves carry sensory information to the CNS; efferent nerves carry motor commands from the CNS.

What are the two main divisions of the Peripheral Nervous System (PNS)?

Sensory (afferent) division and Motor (efferent) division.

What are the two divisions of the motor nervous system?

Somatic nervous system and Autonomic nervous system.

What are the two divisions of the autonomic nervous system?

Sympathetic division and Parasympathetic division.

What neurotransmitter is released by preganglionic neurons in both sympathetic and parasympathetic systems?

Acetylcholine.

What neurotransmitters do postganglionic sympathetic neurons release?

Norepinephrine and epinephrine.

What neurotransmitter do postganglionic parasympathetic neurons release?

Acetylcholine.

What are the steps of a reflex arc?

Sensory receptor -> afferent neuron -> spinal cord -> efferent neuron -> effector.

What are the protective layers and structures of the eye?

Sclera, cornea, iris, pupil, lens, retina, aqueous humor, and vitreous humor.

What are rods and cones?

Photoreceptors in the retina; rods detect low-intensity light for night vision, while cones detect high-intensity light and color.

What is the fovea?

The central area of the retina with the highest cone density for sharpest vision.

What is the blind spot of the eye?

The area where the optic nerve exits the eye, lacking photoreceptors.

How is sound processed in the ear?

Sound waves enter the auditory canal, vibrate the tympanic membrane, are amplified by the ossicles (malleus, incus, stapes), and vibrate the fluid-filled cochlea where hair cells in the Organ of Corti convert them to electrical impulses.

What structures in the inner ear detect balance and head position?

Semicircular canals.