Nervous System Flashcards

Path of Light Through the Eye

Cornea → Aqueous humor → Pupil → Lens → Vitreous humor → Retina (photoreceptors) → Optic nerve → Brain

Path of Sound Through the Ear

Pinna → Auditory canal → Tympanic membrane → Ossicles (malleus, incus, stapes) → Oval window → Cochlea → Auditory nerve → Brain

Sense of Olfaction (Smell)

Olfactory receptor cells in nasal cavity → Olfactory bulb → Olfactory tract → Brain

Sense of Gustation (Taste)

Taste buds on papillae detect chemicals in food → Signals sent via facial, glossopharyngeal, and vagus nerves → Brain

Receptor Cells

Photoreceptor, Mechanoreceptors, Chemosreceptors

• Photoreceptors (eye – light)

rods and cones

Mechanoreceptors

(ear – sound & touch)

• Chemoreceptors

(nose & tongue – smell & taste)

• Rods

low light, black/white

• Cones

color vision, bright light

Cornea

Clear, avascular, and first refractive surface – helps focus light

Blind Spot

No photoreceptors where the optic nerve exits the eye

Refractory Media

Cornea, aqueous humor, lens, vitreous humor – all help bend light

Eye Disorders

Presbyopia, Cataract, Astigmatism, Glaucoma

• Presbyopia

age-related difficulty focusing on close objects

• Cataract

clouding of the lens

• Astigmatism

irregular curvature of cornea/lens

• Glaucoma

increased intraocular pressure, damaging optic nerve

Hearing

Human Hearing Range: 20Hz-20,000Hz

Ceruminous Glands

Produce earwax (cerumen) for protection

Presbycusis

Age-related hearing loss

Papillae/Taste Buds

Structures on tongue containing taste receptors

Dysgeusia

Distorted sense of taste

Anosmia

Loss of smell

Why Mucus & Saliva Matter

• Mucus traps particles & helps olfaction

• Saliva dissolves food chemicals for taste

Cerebral Hemispheres

thought, memory, movement

Diencephalon

relays info, regulates homeostasis

Brain Stem

vital functions (breathing, heartbeat)

Cerebellum

balance and coordination

4 Lobes of Cerebrum

Frontal, Parietal, Temporal, Occipital

• Frontal

reasoning, speech (Broca’s), motor skills

• Parietal

touch, spatial awareness

• Temporal

hearing, memory, language (Wernicke’s)

• Occipital

vision

Diencephalon Parts

Thalamus, hypothalamus, and Epithalamus

Thalamus

sensory relay

Hypothalamus

Homeostasis, Hormones

Epithalamus

Includes pineal Gland

Brain Stem Parts

Midbrain, Pons, Medulla Oblongata

Limbic System

Emotions, memory

• Includes Amygdala and Hippocampus

Amygdala

fear/emotion

Hippocampus

memory

Master Gland

Pituitary

Pineal Body

Produces melatonin (sleep cycle)

Gyri

ridges

Sulci

grooves

Corpus Callosum

Connects left and right hemisphere

CNS

brain & spinal cord

PNS

all other nerves

Synapse

Space between neurons

Neurons

transmit signals

Neuroglia

support neurons

Neuron Types

Unipolar, Bipolar, and Multipolar

• Unipolar

sensory (PNS)

• Bipolar

special senses (eye, nose)

• Multipolar

motor neurons (CNS)

Afferent/Sensory Neurons

Unipolar

Efferent/Motor Neurons

Multipolar

Neuron Anatomy

• Dendrites

receive signals

• Axon

sends signal away

• Soma (Cell Body)

contains nucleus

• Myelin

insulation (made by Schwann cells)

• Neurilemma

outer layer of Schwann cell

• Nodes of Ranvier

gaps for faster conduction

• Axon Terminals

transmit to next neuron

Nerve Transmission Steps

1. Polarization (resting potential)

2. Depolarization (signal sent)

3. Repolarization (returns to rest)

Protection of Brain & Spinal Cord

Meninges and Cerebrospinal Fluid

• Meninges

dura mater, arachnoid mater, pia mater

• Cerebrospinal Fluid (CSF)

cushions, delivers nutrients

Nerves

12 Cranial Nerves, 31 Spinal Nerves

• Cranial Nerve I – Olfactory (smell)

• Cranial Nerve II – Optic (vision)

• Cranial Nerve VIII – Vestibulocochlear (hearing/balance)

Longest Nerve

Vagus nerve

Spinal Cord Ends

L1-L2 (conus medullaris)

Cauda Equina

bundle of spinal nerves at lower end

Blood-Brain Barrier (BBB)

Protects brain; allows O₂, CO₂, glucose; blocks toxins, bacteria

Alcohol

affects cerebellum, frontal lobe, hippocampus

Nicotine

stimulates dopamine → addiction

Marijuana

affects memory (hippocampus), coordination

Aphasia

speech/language disorder

Broca’s Area

speech production (damage = expressive aphasia)

Wernicke’s Area

language comprehension (damage = receptive aphasia)