UNIT 3: The Human Nervous System

Question 1

central nervous system

Answer 1

composed of the brain and spinal cord

Question 2

peripheral nervous system

Answer 2

composed of all the nerves not found within the boundaries of the central nervous system as well as the collections of nerve cells called ganglia.

Question 3

neuron

Answer 3

nerve cell specialised to carry electochemical impulses.

functional unit of the human nervous system

Question 4

sensory neurons

Answer 4

carry impulses towards the central nervous system

Question 5

interneurons

Answer 5

carry impulses from one neuron to another completely within the central nervous system

Question 6

motor neurons

Answer 6

carry impulses from the interneuron to an effector

Question 7

effector

Answer 7

an organ or tissue that carries out an action in response to a signal from the nervous system

Question 8

neuron cell components: dendrites

Answer 8

receive impulses from other neurons and transmit the impulse towards the cell body

Question 9

neuron cell components: cell body

Answer 9

located between the dendrites and axon. it is responsible for the upkeep of the cell and for producing neurotransmitter substances

Question 10

neuron cell components: neurotransmitter

Answer 10

chemical substance released by a neuron to transmit a nerve impulse to another neuron or effector

Question 11

neuron cell components: axon

Answer 11

carries impulses away from the cell body towards axon terminals

Question 12

neuron cell components: myelin sheath

Answer 12

layers of lipids formed from a schwann cell that wrap around the axon and dendrites or neurons. It insulates the axon / dendrite maintaining and speeding up the electrochemical impulse.

Question 13

neuron cell components: schwann cell

Answer 13

produces myelin sheath

Question 14

neuron cell components: axon terminals

Answer 14

present at the end of the axon and contain synaptic vesicles which contain neurotransmitters

Question 15

neuron cell components: synaptic vesicles

Answer 15

contain neurotransmitter chemicals. They fuse with the cell membrane when an impulse reaches the axon terminal. this releases the neurotransmitter

Question 16

nerve impulse

Answer 16

a short-lived electrochemical signal that travels along neurons via movement of chemical ions into and out of the neuron

Question 17

transmission of the nerve impulse to another neuron

Answer 17

occurs at synapses

Question 18

synapses

Answer 18

structure where 2 neurons come into close contact so that a nerve impulse can be transmitted between the 2 neurons

Question 19

transmission process

Answer 19

• nerve impulse arrives at an axon terminal (presynaptic neuron).
• synaptic vesicles are stimulated to fuse with the cell membrane.
• neurotransmitter chemicals are released from the vesicle into the gap between the 2 neurons, called the synaptic cleft; examples of neurotransmitter substances include: acetylcholine, noradrenaline and dopamine.
• once a neurotransmitter is in the synaptic cleft it travels the short distance to the dendrite of the postsynaptic neuron where it stimulates the cell membrane to allow ions to flow inwards, setting up a new electrochemical impulse.
• the neurotransmitter is then either broken down by enzymes or reabsorbed into the presynaptic neuron.

Question 20

functions of the synapse

Answer 20

• allow transmission of the impulse from one neuron to another.
• control the direction of the impulse - the impulse cannot travel backwards.
• acts as junction allowing the impulse to be split up and travel along many different neurons or join many impulses together into one impulse

Question 21

conjunctiva

Answer 21

produces mucous protecting the front of the eye

Question 22

cornea

Answer 22

transparent part of the sclera that protects the front of the eye; it also allows light tot enter the eye and refracts the light rays slightly as part of focusing light into the retina

Question 23

iris

Answer 23

coloured part of the eye.

type of smooth muscle that can contract and relax in response to the amount of light entering the eye

Question 24

pupil

Answer 24

hole in the internal part of the eye just behind the iris. it allows light into the eye and its size is controlled by the iris. it appears black due to light entering and not leaving the eye as it is all absorbed

Question 25

aqueous humour

Answer 25

watery liquid present just inside the cornea that gives shape to the front of the eye

Question 26

vitreous humour

Answer 26

viscous liquid present inside the eye ball that maintains the shape of the eye by maintaining outward pressure on the sclera.

Question 27

ciliary body

Answer 27

type of smooth muscle surrounding the lens that can contract and relax changing the shape of the lens as part of focusing light on the retina

Question 28

suspensory ligament

Answer 28

attaches to and surrounds the ciliary body providing a lever for the contraction of the ciliary muscle

Question 29

lens

Answer 29

transparent structure held in place by the ciliary body and suspensory ligament; changes shape in response to contraction and relaxation of ciliary body. responsible for focusing light on the retina

Question 30

sclera

Answer 30

white of the eye covering the entire eyeball except the front part, protects the eye and acts as the attachment surface for external muscles that move the eye in different directions

Question 31

choroid

Answer 31

heavy pigmented layer lying between the retina and sclera, absorbs all of the light entering the eye and helps to prevent reflection within the eye

Question 32

retina

Answer 32

light-sensitive structure of the eye; contains rods and cones; rods are sensitive to only black and white and cones are sensitive to red, green and blue light.

Question 33

fovea

Answer 33

region of the retina where all of the light rays converge when you look directly at an object, mostly composed of cones

Question 34

blind spot

Answer 34

region of the retina where all the nerve fibres from the retina converge and exit the eye and travel to the brain; there are no light-sensitive cells in this region

Question 35

optic nerve

Answer 35

collection of sensory neurons that carry messages to the brain from the retina

Question 36

long-sightedness (hyperopia): symptom

Answer 36

near objects appear blurred

Question 37

long-sightedness (hyperopia): cause

Answer 37

eyeball is either too short or the focusing elements are too weak

Question 38

long-sightedness (hyperopia): treatment

Answer 38

convex lens placed in front of the eye

Question 39

short-sightedness (myopia): symptom

Answer 39

distant objects appear blurred

Question 40

short-sightedness (myopia): cause

Answer 40

eyeball is either too long or the focusing elements are too strong

Question 41

short-sightedness (myopia): treatment

Answer 41

concave lens in front of the eye

Question 42

outer ear

Answer 42

composed of the pinna and auditory canal. | these pick up sound waves and channel them to the eardrum

Question 43

middle ear

Answer 43

- the sound waves arrive at the eardrum and are transferred into the 3 small bones of the ear - the ossicles - hammer, anvil and stirrup. they transfer sound waves onto the inner ear. they can amplify soft sounds and dampen loud sounds. - the eustachian tube is connected to the throat so that pressure differences can be equalised during swallowing preventing damage to the eardrum

Question 44

inner ear

Answer 44

functions in both hearing and balance | composed of cochlea & vestibular apparatus

Question 45

cochlea

Answer 45

- receives sound vibrations from the ossicles via the oval window. - it is filled with lymph through which the sound waves pass. - there are hair cells within the inner wall of the cochlea that sense the vibrations of the lymph and convert these vibrations into electrical impulses that are then sent to the brain via the auditory nerve. - finally, there is a round window below the oval window that vibrates with an opposite phase to the round window allowing vibrations to be transferred within the lymph more efficiently

Question 46

vestibular apparatus

Answer 46

- consists of 3 semicircular canals filled with lymph. - each canal has hair cells lining its internal walls. - as the head moves, the lymph moves within the canals stimulating the hair cells. - the movement of the lymph is converted into electrical impulses by the hair cells and these impulses are transferred to the brain via the vestibular nerve

Question 47

glue ear: symptom

Answer 47

inflammation of the middle ear, muffled hearing and pus formation

Question 48

glue ear: cause

Answer 48

infections by viruses and/or bacteria

Question 49

glue ear: treatment

Answer 49

ear drops or a grommet for severe infections

Question 50

smell

Answer 50

also called olfaction. occurs in the nasal cavity. there are specialised cells called olfactory receptor cells. this group of cells senses the odours and sends signals to the brain via the olfactory bulb and olfactory nerve

Question 51

taste

Answer 51

5 basic tastes: sweet, sour, salt, bitter & umami.

Question 52

brain

Answer 52

composed of: - cerebrum - cerebellum - medulla oblongata - hypothalamus - pituitary gland

Question 53

cerebrum

Answer 53

- largest part - composed of 2 symmetrical hemispheres. - high folded surface giving extra area for neurons. - divided into different lobes: frontal, temporal, parietal, occipital

Question 54

frontal lobe

Answer 54

functions in reasoning, short-term memory, intelligence, personality, problem-solving, emotion & language.

Question 55

temporal lobe

Answer 55

functions in long-term memory, speech & hearing

Question 56

parietal lobe

Answer 56

functions in movement & touch

Question 57

occipital lobe

Answer 57

functions in vision

Question 58

cerebellum

Answer 58

- located at the back of the brain | - functions in control and coordination of movement.

Question 59

medulla oblongata

Answer 59

- belongs to the brainstem (on top of the spinal cord). | - functions in breathing, heart rate, blood pressure, vomiting, coughing, sneezing & swallowing

Question 60

hypothalamus

Answer 60

- small region of the brain located just above the brain stem and pituitary. - functions in controlling the endocrine system via secretion of neurohormones such as growth hormone-releasing hormone (GHRH) and thyrotropin-releasing hormone (TRH). - it also functions in controlling body temperature, hunger and thirst

Question 61

pituitary gland

Answer 61

- the link between the nervous system and the endocrine system - it releases many hormones including: growth hormone (GH) and thyroid-stimulating hormone (TSH).

Question 62

parkinsons disease: cause

Answer 62

death of specific neurons deep within the brain. | the reasons for the death of these neurons is unknown but thought to be caused by exposure to pesticides.

Question 63

parkinsons disease: symptoms

Answer 63

shaking and trembling of the hands, arms and legs during movement, a stiff and rigid body and fixed stare.

Question 64

parkinsons disease: treatment

Answer 64

physiotherapy, exercise and a drug called levodopa

Question 65

the spinal cord

Answer 65

- a bundle of nerve fibres enclosed within the spine, covered in specialised membranes called meninges and bathed in cerbrospinal fluid. - it carries messages to and from the brain. - it has 31 pairs of spinal nerves. - there are structures called the dorsal root, dorsal root ganglion and a ventral root associated with each spinal nerve. - the dorsal root carries sensory neurons - the dorsal root ganglion contains the cell bodies of those sensory neurons. - the ventral root carries the motor neurons. - spinal cord is composed of white matter and grey matter. outer region = white. inner = grey. - there is a central canal filled with cerebrospinal fluid.

Question 66

reflex action

Answer 66

involuntary responses to a stimulus. - carried out by reflex arcs. - reflex arcs consist of a sensory neuron, an interneuron and a motor neuron. - a common reflex action is the withdrawal reflex - touch something hot = pull hand away. - the sensory neuron detects that something hot has been touched and sends a message to the spinal cord via the dorsal root. - the sensory neuron synapses with an interneuron just inside the grey matter of the spinal cord and passes the message on. - the interneuron relays the message onto the motor neuron, whose cell body is just inside the grey matter of the spinal cord. - the motor neuron sends a message out through the ventral root to the skeletal muscles of the arm to pull the hand away from the hot object.

Question 67

nervous system vs endocrine system: NERVOUS

Answer 67

``` speed of response: fast messages carried by: electrochemicals (ion movement) speed of transmission of message: fast length of response: short-lived areas affected: specific areas ```

Question 68

nervous system vs endocrine system: ENDOCRINE

Answer 68

``` speed of response: slow messages carried by: chemical hormones speed of transmission of message: slow length of response: long-lived areas affected: wide areas ```

Question 69

Ganglion

Answer 69

A group of cell bodies located outside the central nervous system

Question 70

Threshold

Answer 70

The minimum stimulus needed to cause an impulse to be carried in a neuron

Question 71

All or nothing law

Answer 71

States that if the threshold is reached an impulse is carried, but if the threshold is not reached no impulse is carried

Question 72

Refractory period

Answer 72

A short time span after a neuron has carried an impulse during which a stimulus fails to cause a response

Question 73

Synaptic cleft

Answer 73

A tiny gap between the two neurons at a synapse

Question 74

Reflex arc

Answer 74

The pathway taken by a nerve Impulse in a reflex action