The Nervous System

Question 1

What is homeostasis?

Answer 1

The body’s ability to maintain a stable internal environment despite external changes.

Question 2

What is the central nervous system (CNS) composed of?

Answer 2

The brain and spinal cord.

Question 3

What is the peripheral nervous system (PNS) composed of?

Answer 3

All nerves outside the CNS that connect the brain/spinal cord to the rest of the body.

Question 4

What is the difference between somatic and autonomic nervous systems?

Answer 4

Somatic controls voluntary movements (skeletal muscles); Autonomic controls involuntary functions (organs, glands, smooth muscle).

Question 5

What are the two divisions of the autonomic nervous system?

Answer 5

Sympathetic (“fight or flight”) increases heart rate and energy use, while parasympathetic (“rest and digest”) slows heart rate and promotes relaxation.

Question 6

What is a reflex arc?

Answer 6

A fast, automatic response to a stimulus that bypasses the brain and is processed in the spinal cord.

Question 7

What are the five steps of a reflex arc?

Answer 7

1. Stimulus detected by receptors.
2. Sensory neuron sends a signal to the spinal cord.
3. Interneuron processes the signal.
4. Motor neuron sends a response to muscles.
5. Effector (muscle/gland) reacts (e.g., pulling hand away from heat).

Question 8

Why do reflexes protect the body?

Answer 8

They reduce reaction time and prevent injury by responding instantly before the brain processes the danger.

Question 9

What is sensory adaptation?

Answer 9

When sensory receptors stop responding to an unchanging stimulus (e.g., getting used to a strong perfume).

Question 10

What are the four types of sensory receptors?

Answer 10

• Photoreceptors – Detect light (in the retina).
• Chemoreceptors – Detect chemicals (taste buds, olfactory cells).
• Mechanoreceptors – Detect touch, sound, and balance (skin, ear).
• Thermoreceptors – Detect temperature changes (skin, hypothalamus).

Question 11

What is the role of proprioceptors?

Answer 11

Detect body position and movement in muscles, tendons, and joints to help with balance and coordination.

Question 12

What are the three layers of the eye?

Answer 12

Sclera (outer) – Protects and maintains shape.
Choroid (middle) – Supplies blood, absorbs stray light.
Retina (inner) – Contains rods and cones for vision.

Question 13

What is the function of the lens?

Answer 13

Focuses light onto the fovea centralis for sharp vision.

Question 14

What is accommodation?

Answer 14

The lens changes shape to focus on near or far objects.

Question 15

What do rods and cones detect?

Answer 15

Rods detect black and white, dim light; Cones detect color and bright light.

Question 16

What causes the blind spot?

Answer 16

The optic disc, where the optic nerve leaves the eye, has no photoreceptors.

Question 17

What are common vision disorders?

Answer 17

• Astigmatism – Irregular cornea, causing blurry vision.
• Myopia (nearsightedness) – Light focuses in front of retina.
• Hyperopia (farsightedness) – Light focuses behind retina.

Question 18

What are serious eye diseases?

Answer 18

• Glaucoma – Increased eye pressure damages optic nerve.
• Cataracts – Clouding of the lens, blocking light.
• Retinal Detachment – Retina separates, causing vision loss.
• Macular Degeneration – Damage to fovea centralis, affecting central vision.

Question 19

What are the three parts of the ear?

Answer 19

• Outer Ear – Collects sound (pinna, auditory canal).
• Middle Ear – Amplifies vibrations (eardrum, ossicles).
• Inner Ear – Converts vibrations into nerve signals (cochlea, hair cells).

Question 20

How do we hear sound?

Answer 20

1. Sound waves enter the ear canal.
2. Eardrum vibrates and moves ossicles.
3. Ossicles amplify sound and pass it to the cochlea.
4. Hair cells in the cochlea detect movement and send signals to the brain.

Question 21

What causes hearing loss?

Answer 21

• Nerve Deafness – Damage to cochlea’s hair cells (permanent, caused by loud noise or aging).
• Conduction Deafness – Blockage in outer/middle ear (earwax, infections, ossicle damage).

Question 22

How does the ear help with balance?

Answer 22

• Semicircular canals detect head rotation.
• Utricle & Saccule detect tilt and gravity.
• Otoliths (tiny crystals) shift to stimulate hair cells, sending signals to the brain.

Question 23

What are the main touch receptors?

Answer 23

• Light touch receptors – Detect soft contact.
• Pressure receptors – Detect firm touch/squeezing.
• Pain receptors (nociceptors) – Detect injury/damage.
• Thermoreceptors – Detect temperature changes.

Question 24

What type of receptors are in taste buds?

Answer 24

Chemoreceptors detect dissolved food particles for sweet, sour, salty, bitter, and umami flavors.

Question 25

How does smell work?

Answer 25

Olfactory receptors in the nasal cavity detect airborne chemicals and send signals to the olfactory bulb in the brain.

Question 26

Why are taste and smell linked?

Answer 26

80-90% of taste perception comes from smell, which is why food tastes bland when you have a cold.

Question 27

What is a neuromuscular junction?

Answer 27

The synapse between a motor neuron and a muscle where acetylcholine triggers muscle contraction.

Question 28

What happens if the dorsal root of a spinal nerve is severed?

Answer 28

The body cannot detect sensory stimuli, so the reflex arc won’t be triggered.

Question 29

What happens if the ventral root is severed?

Answer 29

The muscle won’t receive motor signals, so it can’t respond to stimuli.

Question 30

Which type of neuron carries impulses toward the CNS?

Answer 30

Sensory neurons (afferent neurons).

Question 31

What part of the brain controls balance, posture, and coordination?

Answer 31

Cerebellum.

Question 32

What are the first and last elements in a reflex arc?

Answer 32

First: Sensory receptor, Last: Effector (muscle/gland).

Question 33

How does a nerve impulse cross a synapse?

Answer 33

A neurotransmitter is released from the axon of the pre-synaptic neuron to the dendrite of the post-synaptic neuron.

Question 34

What are the two divisions of the autonomic nervous system?

Answer 34

Sympathetic ("fight or flight") & Parasympathetic ("rest and digest").

Question 35

A patient with a blockage at a sensory neuron’s entry point in the spinal cord can still move their hand but can’t feel pain. Why?

Answer 35

Sensory signals can’t reach the brain, but motor signals are unaffected.

Question 36

Where does paraplegia occur?

Answer 36

At or below the T1 thoracic level, affecting the lower body.

Question 37

Where does quadriplegia occur?

Answer 37

In the cervical region, affecting the arms, legs, and trunk.

Question 38

Which part of the brain maintains homeostasis (hunger, thirst, body temp)?

Answer 38

Hypothalamus.

Question 39

Which brain structure connects the left and right hemispheres?

Answer 39

Corpus Callosum.

Question 40

What is the function of the thalamus?

Answer 40

Relays sensory information to the correct part of the brain for processing.

Question 41

Which neurotransmitter is low in Parkinson’s disease?

Answer 41

Dopamine

Question 42

How do drugs like Levadopa and Seligiline help Parkinson’s disease?

Answer 42

Levadopa replaces missing dopamine, while Seligiline prevents dopamine breakdown.

Question 43

How do opiate drugs like heroin affect the brain?

Answer 43

They bind to mu and delta receptors, increasing dopamine and creating a euphoric effect.

Question 44

What structure regulates how much light enters the eye?

Answer 44

Iris

Question 45

Which eye disorder occurs when the cornea or lens has an uneven curvature?

Answer 45

Astigmatism

Question 46

Which eye disorder is caused by an eyeball that is too long?

Answer 46

Myopia (nearsightedness).

Question 47

Which disorder involves abnormal blood vessel growth in the retina, leading to vision loss?

Answer 47

Diabetic Retinopathy.

Question 48

What structure in the ear is responsible for maintaining equilibrium?

Answer 48

Semicircular canals & vestibule (utricle and saccule)

Question 49

Which ear structure helps equalize air pressure?

Answer 49

Eustachian tube

Question 50

How does a cochlear implant help with hearing loss?

Answer 50

It bypasses damaged hair cells and directly stimulates the auditory nerve.

Question 51

What happens to a neuron’s charge when an action potential starts?

Answer 51

Inside becomes positive (depolarization) as sodium (Na⁺) enters.

Question 52

What happens to dopamine levels when cocaine is used?

Answer 52

Dopamine remains in the synapse longer, increasing its effects.

Question 53

What happens in a sympathetic nervous system response?

Answer 53

Heart rate increases, pupils dilate, and norepinephrine is released.

Question 54

What happens in a parasympathetic nervous system response?

Answer 54

Heart rate decreases, pupils constrict, and acetylcholine is released.

Question 55

What is a synapse?

Answer 55

A small gap between neurons where nerve signals are transmitted chemically using neurotransmitters.

Question 56

What are the three parts of a synapse?

Answer 56

Presynaptic neuron (sends signal), synaptic cleft (gap), and postsynaptic neuron (receives signal).

Question 57

What happens when an action potential reaches the axon terminal?

Answer 57

Calcium (Ca²⁺) channels open, triggering neurotransmitter release into the synaptic cleft.

Question 58

How do neurotransmitters cross the synapse?

Answer 58

They diffuse across the cleft and bind to specific receptors on the postsynaptic neuron.

Question 59

What happens after neurotransmitters bind to receptors?

Answer 59

Ion channels open, triggering a response (excitatory or inhibitory)

Question 60

How is the synaptic signal stopped?

Answer 60

Neurotransmitters are removed via reuptake, enzymatic breakdown, or diffusion

Question 61

What is reuptake?

Answer 61

The presynaptic neuron reabsorbs neurotransmitters to stop the signal and recycle them.

Question 62

What does acetylcholine (ACh) do at the neuromuscular junction?

Answer 62

It triggers muscle contraction by binding to receptors on muscle cells.

Question 63

How do drugs affect synaptic transmission?

Answer 63

Some enhance neurotransmitter effects (e.g., cocaine blocks dopamine reuptake), while others inhibit them (e.g., Botox blocks ACh release).

Question 64

How do SSRIs (Selective Serotonin Reuptake Inhibitors) treat depression?

Answer 64

They block serotonin reuptake, keeping more serotonin in the synapse to improve mood.