The Nervous System

AB Highschool bio30 Nervous system (unit 1)

Soma

Houses important cell bits like the mitochondria

Nucleus

The brain of the neuron Holds genetic data for protein synthesis Houses and builds DNA

Dendrites

Receivers of the neurotransmitters’ electrical signals from other neuron (axon terminals)

Myelin Sheath

Protects and insulates the axon Allows for efficient and quick transport impermeable to Na+ (sodium)

Node of Ranvier

Spots where Na+ (sodium) can enter and cause a nerve impulse (action potential)

Axon

Part that carries electrical signals away from the soma and towards other neurons

Axon Terminal & Bulb

Place where the electrical signals depart from on the neuron (via neurotransmitters)

Neurons

Cells specialized in conducting nerve/electrical signals over long distances

Central Nervous System

Home of the brain and spinal cord. Where your body processes sensory information and turns it into decisions. Also the only place that conscious thought happens. Houses interneurons

Peripheral nervous system

Everything around the central nervous system. Sensory and motor neurons are housed here. Where you sense everything.

Grey matter

Unmyelinated neurons. Surround the brain, covered with fissures (folds)

White matter

Myelinated neurons, inside the brain. Faster transport.

Forebrain

Cerebrum, thalamus, hypothalamus

Midbrain

Tectum, tegmentum

Hindbrain

Pons, cerebellum, medulla oblongata

Frontal lobe

Conscious thought, memory, intelligence, personality, Broca's area, voluntary muscle movements

Parietal lobe

Somatosensory functions (touch, taste), processes info about body position

Occipital lobe

Processes visual information

Temporal lobe

Auditory reception (hearing) & memory, Wernicke s area (language comprehension)

Cerebellum

Limb movements, balance, muscle tone

Pons

Relay station between cerebrum and cerebellum

Medulla oblongata

Autonomic nervous system, connection between PNS & CNS

Hypothalamus

Regulates the pituitary gland, keeps body in homeostasis with autonomic system & hormones

Corpus collosum

Communication between hemispheres, a bundle of nerves

Cerebrum

Complex thought, hemispheres are connected by a bundle of nerves

Paraplegia

Injury below the first thoracic vertebrae, paralysis generally @legs

Quadriplegia

Injury of spinal cord close to neck, paralysis to most of body

Myelinated neurons

White matter of brain, conducts nerve impulses, can regenerate after injury

Polarized/resting state

Inside cell voltage → - 70 mV RMP, inside cell ↑ [K+] outside cell ↑[ Na+] (like a salty banana!) 🍌

Sodium-Potassium pumps move 3 Na+ inside and 2 K+ outside to maintain -70mV (K+ leaks out through channels 😓)

Depolarization

Stimulus arrives!

Impulse causes sodium gates to open

Sodium (Na+) floods in

Membrane potential goes -70mV → +40mV

All or nothing (has to reach -55mV)

Na+ gates close @ equilibrium

Repolarization

Trying to get back to normal

K+ gates (@ protein channels) open

Na+ and K+ concentrations have switched

Sodium-potassium pumps kick in to switch the Na+ and K+ back to original spots

• trying to re-establish -70mV

Refractory period

SUPER rest

Time to get ready again

Sodium-potassium pump overshoots → -90mV

Recovery → gives it a chance to rest

• pumps slow down

• Na+ and K+ diffuse

Thermoreceptors

Stimulated by heat/cold (skin receptors)

Nocireceptors

Sense pain

Somatic

Voluntary control, carries info from sensory receptors to skeletal muscles, external stimuli

Autonomic

Involuntary control, maintains homestasis (breathing, heart rate, peristalsis), internal stimuli

Sympathetic nervous system

Fight or flight, release of epinephrine/noepinephrine

Parasympathetic

Rest & digest & reproduce, activated when body is at rest, release of acetylcholine

Sclera

Protects eye’s inner layers, maintains eye shape

Cornea

Transparent part that protects the eye, refracts light toward pupil

Choroid layer

Blood vessels that nourish the retina

Iris

Regulates amount of light into eye

Pupil

Opening formed by iris → allows light into eye

Ciliary muscles

Alter shape of lens → adjust focus

Rods

Photoreceptors, detect light in black & white

Dim light

Cones

Photoreceptors, colour, bright light

Fovea centralis

Area where cones are most dense/vision is sharpest

Lens

Focuses light onto retina

Aqueous humor

Maintains shape of cornea

Vitreous humor

Maintains eyeball shape

Optic nerve

Carries impulse (vision-based) to CNS

Ganglion layer

Forms optic nerve that exits back of eye (blind spot)

Astigmatism

Eyeball shape changes the way that the light focuses on retina (improperly refracts the light )

Myopia

Nearsightedness, eyeball is elongated. Focused light falls in front of the retina, can't see stuff far

Hyperopia

Farsightedness (can't see close stuff), eyeball is shortened (focused light falls beyond retina)

Colourblindness

Lack of specific cones ( colour receptors)

Pinna

Direct sound waves to the auditory canal (funnel them)

Auditory canal

Passage for sound waves toward the midear

Tympanic membrane ( tympanum/eardrum )

Pass on vibrations to the ossicles

Ossicles

Malleus, incus, stapes -- amplify the sound waves

Semicircular canals

Sense 3D position & maintain balance. Filled with fluid

Eustachean tube

Allows air pressure to equalize. Tube that connects to throat

Auditory nerve

Sends the action potential (produced by stereocilia in the Organ of Corti)

Cochlea

Where the Organ of Corti is. (i.e, where a nerve impulse/action potential is generated!)

Vestibule

Carry amplified signal from the oval window and sends it to the cochlea

Organ of Corti

Where the stereocillia are housed (where the action potential is actually generated)

Oval window

Turns vibration by ossicles into pressure changes in the inner ear

Olfactory bulb

Processes smells