Nervous System & Reflex Arcs

The nervous system's functions include sensory input, integration, control of muscles and glands, homeostasis, and mental activity.

The peripheral nervous system includes all nerve tissue outside the brain and spinal cord.

Afferent neurons transmit sensory information from receptors to the central nervous system.

Efferent neurons transmit motor commands from the central nervous system to effectors (muscles/glands).

Dendrites receive signals from other neurons.
The Soma (cell body) contains the nucleus and integrates signals.
The Axon transmits signals away from the soma.
The Myelin Sheath insulates the axon, speeding up signal transmission.
Nodes of Ranvier are gaps in the myelin sheath that allow for rapid conduction.
Axon Terminals are the ends of the axon that transmit signals to other neurons or cells.
The Synapse is the junction between two neurons where signals are transmitted.
Neurotransmitters are chemicals that transmit signals across the synapse.

During its resting state, a neuron has a negative charge inside compared to the outside, called the resting membrane potential.
Maintained by ion pumps and differential permeability to ions.

Depolarization occurs when the membrane potential becomes more positive due to influx of sodium ions.
Threshold is the level of depolarization required to trigger an action potential.
Repolarization occurs as potassium ions flow out, restoring the negative membrane potential.
Hyperpolarization is a brief period where the membrane potential is more negative than the resting state.

The pathway for voluntary motion involves the brain making a decision, which then sends a signal down the spinal cord to motor neurons, which then activate muscles.
Reflex pathways involve sensory neurons sending signals to the spinal cord, which then directly activate motor neurons bypassing the brain.

The Frontal Lobe controls higher-level cognitive functions like reasoning, planning, and motor control.
The Parietal Lobe processes sensory information like touch, temperature, and pain.
The Temporal Lobe is responsible for auditory processing, memory, and language comprehension.
The Occipital Lobe is responsible for visual processing.
The Cerebellum coordinates movement and balance.
The Brain Stem controls basic life functions like breathing and heart rate.

The layers of protection for the central nervous system include the skull/vertebrae, meninges (dura mater, arachnoid mater, pia mater), and cerebrospinal fluid.

The Cornea is the transparent outer layer that focuses light.
The Pupil is the opening that controls the amount of light entering the eye.
The Iris is the colored part of the eye that adjusts the size of the pupil.
The Lens focuses light onto the retina.
The Vitreous Humor is the gel-like substance that fills the space between the lens and retina.
The Retina contains photoreceptors that detect light and convert it into electrical signals.
The Optic Nerve transmits signals from the retina to the brain.
The Sclera is the white outer layer of the eye that provides protection.

20/20 vision means that at 20 feet, you can see what a person with normal vision can see at 20 feet.
20/15 vision is better (you can see at 20 feet what a normal person sees at 15 feet).
20/30 vision is worse (you can see at 20 feet what a normal person sees at 30 feet).

Depth perception is the ability to judge the distance of objects.
Achieved through binocular cues (using both eyes) and monocular cues (using one eye).

Conductive hearing loss is caused by problems with the outer or middle ear that prevent sound from reaching the inner ear.
Sensorineural hearing loss is caused by damage to the inner ear or auditory nerve.
Conductive hearing loss affects the outer and middle ear parts.
Sensorineural hearing loss affects the inner ear parts.

The Pinna (auricle) collects sound waves.
The Auditory Canal transmits sound waves to the tympanic membrane.
The Tympanic Membrane (eardrum) vibrates in response to sound waves.
The Auditory Ossicles (malleus, incus, stapes) amplify and transmit vibrations to the oval window.
The Cochlea converts vibrations into electrical signals.
The Auditory Nerve transmits signals from the cochlea to the brain.