Human Bio Ch 4

Question 1

What are the 3 main sources of protection for the CNS?

Answer 1

1. Bones (cranium and vertebral canal)
2. Membranes called meninges
3. Cerebrospinal fluid

Question 2

What are 3 layers of meninges and what is their structure?

Answer 2

1. Outer layer = dura mater, tough and fibrous, sticks closely to the bones of the skull, texture similar to rubber gloves.
2. Middle layer = arachnoid mater, loose mesh of fibres.
3. Inner layer = pia mater, far more delicate, contains many blood vessels and sticks closely to the brain and spinal cord.

Question 3

What is are the main functions of cerebrospinal fluid?

Answer 3

Occupies the space between the arachnoid mater and pia mater. Is clear and watery containing a few cells, glucose, protein, urea and salt. Main functions:
1. Protection = acts a shock absorber
2. Support = brain is suspended inside cranium and float in fluid surrounding it
3. Transport = carries nutrients to the cells of the brain whilst taking away their wastes.

Question 4

What are the 5 main parts of the brain?

Answer 4

1. Cerebrum
2. Corpus callosum
3. Cerebellum
4. Hypothalamus
5. Medulla oblongata

Question 5

What is the cerebrum and what does it contain?

Answer 5

Cerebrum is the largest part of the brain, the surface is folded into convolutions. It is made up up of grey matter known as the cerebral cortex that consists of neuron cell bodies, dendrites and unmyelinated axons, below this is the white matter which is made up of myelinated axons.

The convolutions greatly increase surface area and contain, shallow downfolds called sulci and deeper downfolds called fissures. The deepest fissure called the longitudinal fissure separates the cerebrum in two hemispheres (left and right).

Question 6

What are the main lobes of the brain that are found in the cerebrum? (x5)

Answer 6

1. Frontal = thinking, problem solving, emotions, personality, language, and control of movement
2. Parietal = processing temperature, touch, taste, pain and movement
3. Temporal = processing memories and linking them senses, receives auditory information
4. Occipital = vision
5. Insula = recognition of different senses and emotions

Question 7

What are the three functional areas of the cerebral cortex?

Answer 7

1. Sensory areas = interpret impulses from receptors
2. Motor areas = control muscular movements
3. Association areas = intellectual and emotional processes

Question 8

What is the corpus callosum?

Answer 8

Is a wide band of nerve fibres that lies underneath the cerebrum at the base of the longitudinal fissure. Nerve fibres from the corpus callosum cross from one hemisphere to the other and allows the two sides to communicate with each other.

Question 9

What is the cerebellum?

Answer 9

Lies under the rear part of the cerebrum. It is the second largest part of the brain and its surface is folded into a series of parallel ridges. The outer folded parts are grey matter and inside is white matter that branches to all parts of the cerebellum. Controls posture, balance and fine coordination of voluntary muscle movements. If damaged we would have spasmodic, jerky and uncontrolled movements.

Question 10

What is the hypothalamus?

Answer 10

Lies in the middle of the brain and cannot be seen from the outside. Controls many bodily activities but it is most concerned with maintaining a constant internal environment (homeostasis).

Question 11

What is the medulla oblongata?

Answer 11

It is a continuation of the spinal cord. Many nerve fibres simply pass through the medulla oblongata going to or from the other parts of the brain. Plays a vital role in automatically adjusting body functions. Contains:
1. cardiac centre - regulates rate and force of the heart beat
2. respiratory centre - controls rate and depth of breathing
3. vasomotor centre - regulates the diameter of blood vessels

Question 12

What does the spinal cord do?

Answer 12

Provides a pathway for communication between muscles and glands and the brain. Contains ascending tracts that are sensory axons that carry impulses upwards towards the brain and descending tracts that contain motor axons that conduct impulses downwards away from the brain.

Question 13

What are the 2 types of nerves?

Answer 13

1. Cranial nerves = 12 pairs of nerves that arise from the brain. Most cranial nerves are mixed nerves meaning they contain fibres that carry nerves into the brain ( sensory fibres) and out of the brain (motor fibres)
2. Spinal nerves = 31 pairs of nerves that arise from the spinal cord, they are all mixed nerves containing both sensory and motor fibres. Each nerve is connect via 2 roots the ventral root and dorsal root.

Question 14

What are the 2 main divisions of the peripheral nervous system?

Answer 14

1. Afferent division
2. Efferent division

Question 15

What is the afferent division and what can it be divided into?

Answer 15

Afferent division of the PNS has fibres that carry nerve impulses into the CNS by sensory neurons from receptors in the skin and around muscles and joints. Further divided into:
1. Somatic sensory - brings impulses from the skin and muscles
2. Visceral sensory - brings impulses from the internal organs

Question 16

What is the efferent division and what can it be divided into?

Answer 16

Contains fibres that carry impulses away from the CNS. Divided into:
1. Somatic division = takes impulses from the CNS to the skeletal muscles
2. Autonomic division = takes impulses from the CNS to the heart muscle and involuntary muscles and gland.

The autonomic division is further divided into:
1. Sympathetic division - produces fight or flight responses
2. Parasympathetic division - maintains during the bodies quiet time.

Question 17

What is the fight or flight response?

Answer 17

A response that prepares the body for increased activity brought about by the stimulation of the sympathetic division of the autonomic nervous system.
Sympathetic division causes the body to:
- increase heart rate and strength of contraction
- dilate bronchioles in the lungs
- decrease movement in the stomach
- increase breakdown of glycogen and release of glucose in liver
- dilate pupils
- increase sweat secretion
- decrease secretion of saliva
- constricts blood vessels in the skin
- dilates blood vessels in the skeletal muscles
- constricts blood vessels in organs apart from heart and lungs
- stimulates the release of adrenaline from the adrenal medulla
The PARASYMPATHETIC division does the OPPOSITE to these.