The Nervous System

Question 1

Central Nervous System

Answer 1

• made up of the brain, spinal cord, and the retina of the eye
• protected by the skull, meninges (layers of tissue), and cerebral spinal fluid
• 31 segments of the spinal cord, a pair of spinal nerves extends from each segment into the body

Question 2

Peripheral Nervous System

Answer 2

• 43 pairs of nerves which connect the body to the CNS
• made up of sensory neurons, which receive stimuli, and motor neurons, which respond to stimuli
• broken down into somatic and autonomic nervous systems

Question 3

Somatic Nervous System

Answer 3

• voluntary, controlled consciously; e.g. movement of muscles
• communicates with sense organs and voluntary muscles
• broken down into sensory (afferent) and motor (efferent) nervous systems

Question 4

Sensory Nervous System

Answer 4

• afferent

- sensory input

Question 5

Motor Nervous System

Answer 5

• efferent

- motor output

Question 6

Autonomic Nervous System

Answer 6

• involuntary, controls unconscious impulses; e.g. heart beat
• communicates with internal organs and glands
• broken down into the sympathetic and parasympathetic nervous systems

Question 7

Sympathetic Nervous System

Answer 7

• arousing

- speeds up heart rate and breathing, raises blood pressure, stops digestive activity

Question 8

Parasympathetic Nervous System

Answer 8

• calming

- slows down heart rate and breathing, lowers blood pressure, resumes digestive activity

Question 9

Reflex

Answer 9

• rapid, unlearned, involuntary response to a stimulus, e.g. sneezing, coughing, blinking, ducking, dilation of pupils
• protect people from injury or deal with things that require immediate attention

Question 10

Receptors (reflex)

Answer 10

• located in skin or sense organs

- detect stimulus, create impulse

Question 11

Sensory neuron (reflex)

Answer 11

• conducts nerve impulses towards the CNS

- carries messages from a receptor to the spinal cord, this is called the afferent pathway

Question 12

Interneuron (reflex)

Answer 12

• connect sensory and motor neurons
• carry messages from sensory to motor neurons
• transmit signals up the spinal cord to the brain, where they are perceived as pain

Question 13

Motor neurons (reflex)

Answer 13

• conduct nerve impulses from the CNS to an effector

- carries messages from the spinal cord to an effector, called the efferent pathway

Question 14

Effector (reflex)

Answer 14

• responds to impulses by contracting (if a muscle fibre) or secreting enzymes or hormones (if a gland)

Question 15

Neuron

Answer 15

• functional cell of the nervous system
• sends and receives nerve impulses
• 100 billion on the brain’s surface
• 10% of cells in brain

Question 16

Dendrites

Answer 16

• short

- receive nerve impulses

Question 17

Axon

Answer 17

• long

- send nerve impulses away from the cell body

Question 18

Myelin sheath

Answer 18

• Schwann cells (fatty tissue) that wraps around axons, enabling impulses to be sent quickly

Question 19

Cell body

Answer 19

• dendrites and the axon are connected to the cell body

- contains nucleus

Question 20

Axon terminal

Answer 20

• end of axon

- stores vesicles which contain neurotransmitters

Question 21

Nodes of Ranvier

Answer 21

• gaps in myelin sheath

Question 22

Synapses

Answer 22

• small gap present between the end of an axon on one neuron and the dendrite or cell body of another neuron
• where neurotransmitters diffuse

Question 23

Action potential

Answer 23

1. Stimulus causes change in permeability
2. Na voltage gated channels open, Na ions diffuse into neuron, beginning action potential
3. Interior of cell is now positively charged, exterior negatively charged
4. Na channels close, K channels open
5. K ions diffuse outside of cell, reversing charges again, and signalling the end of action potential
6. Na and K ions are pumped through sodium potassium pump to return to resting potential (Na goes out, K goes in)

Question 24

Neurotransmitters

Answer 24

• vesicles containing neurotransmitters fuse with the presynaptic membrane when action potential reaches the axon terminal
• fusion releases neurotransmitter molecules into synaptic cleft
• molecules diffuse across the synaptic cleft, bind with receptor molecules in the post-synaptic cleft
• this changes permeability of the post-synaptic membrane/opens ion channels

Question 25

Forebrain

Answer 25

• functions include receiving and processing information, thinking, perceiving, producing and understanding language, and controlling motor function
• most of the actual information processing in the brain takes place in the cerebral cortex

Question 26

Midbrain

Answer 26

• involved in auditory and visual responses as well as motor function

Question 27

Hindbrain

Answer 27

• assists in maintaining balance and equilibrium, movement coordination, and the conduction of sensory information
• contains the medulla oblongata, responsible for controlling autonomic functions (breathing, heart rate, digestion, etc.)
• oldest and most basic part of the brain

Question 28

Limbic System

Answer 28

emotional control centre of the brain