Chp 4 Nervous System - Human Bio

What is the Central Nervous system derived of and what is its purpose?

• Brain

• Spinal Cord

• Incoming messages are processed and outgoing messages are initiated

What three structures protect the CNS?

• bone (cranium & vertebrae)

• Meninges

• Cerebrospinal fluid

Where is the cranium located?

• outermost protective layer

• Part of skull that houses the brain

Where is the vertebral canal?

• opening in the vertebrae

• Spinal cord runs through

How do bones protect the CNS?

• provide strong rigid structure to protect structures underneath

What are meninges and how many layers are there?

Membranes of connective tissue

3 layers: Dura mater (outer), Arachnoid mater (middle), Pia mater (inner)

What is the outer meningeal layer?

Dura mater

• tough and fibrous

• Provides layer of protection for brain

• Sticks closely to cranium, but on inside of vertebral canal not so close fitting

What is the middle meningeal layer?

Arachnoid mater

• loose mech of fibres

What is the inner meningeal layer?

Pia mater

• more delicate

• Contains many blood vessels and sticks closely to surface of brain and spinal cord

What is Cerebrospinal fluid?

Clear, watery fluid containing a few cells and some glucose, protein, urea, and salts

Where is the cerebrospinal fluid located?

• Occupies space between middle & inner layers of meninges

• circulates through cavities in brain

• Also through canal in centre of spinal cord

What are the three functions of CSF

• Protection: acts as shock absorber, cushioning any blows or shocks CNS may sustain

• Support: brain suspended inside cranium and floats in fluid that surrounds it

• Transport: CSF formed from blood and circulates around and through CNS before eventually re-entering blood capillaries

• → during its circulation, takes nutrients to cells of brain and spinal cord and carries away their wastes

What is the Cerebrum?

• biggest part of brain

• Has outer grey matter known as cerebral cortex ~2-4mm

• Inside is white matter

• Deep inside is additional grey matter - Basal ganglia

What is grey matter made of?

• neuron cell bodies

• Dendrites

• Unmyelinated axons

What is white matter made of?

• myelinated axons

How is the cerebral cortex structured?

• folded in patters to greatly increase its surface area

• Contains 70% of all neurons in CNS

What do the folds of the cerebral cortex produce?

Rounded ridges called: Convolutions (gyri, singular: gyrus)

• → convolutions separated by either shallow downfolds: sulcus, or deep downfolds: fissures

How is the cerebrum structured?

2 halves

• left & right cerebral hemispheres

• Longitudinal fissure separates them

• Deep inside is Insula

What are the different lobes? And how are they formed?

5 lobes

• Frontal, temporal, occipital, parietal, insula

• Fissures and soul I used to further subdivide cerebral hemisphere into lobes

What is the frontal lobes function?

• thinking, problem solving

• Emotions, personality, language

• Control of movement

What is the parietal lobes function?

• processing temperature, touch, taste, pain and movement

What is the temporal lobes function?

• processing memories & linking them with sense

• Receiving auditory information

What is the occipital lobes function?

• vision

What is the Insulas function?

• recognition of different sense & emotions

• Addiction & psychiatric disorders

What is the cerebral cortex responsible for?

• Mental activities: thinking, reasoning, learning, memory, intelligence, sense of responsibility

• Concerned with perception of senses

• Initiation & control of voluntary muscle contraction

How are impulses tied to the cerebral cortex?

• nearly all impulses from sense organs are carried to cerebral cortex

• Has all relevant info about environment

• → can initiate response accordingly

How is the cerebral cortex divided?

1. Sensory areas : interpret impulses from receptors

2. Motor areas : control muscular movements

3. Association areas : concerned with intellectual & emotional processes, also involved in memory

What is memory like in the brain?

Memories not stored in individual memory cells, but are pathway of neurons

When memory is stored, new links made between neurons or existing links are modified

How are the left and right cerebral hemispheres different?

Left controls right, right controls left

Left: language, logical reasoning, analytical, speech

Right: artistic & musical abilities, imagination etc.

What are bundles of nerve fibres called?

In CNS: tracts

Outside Nerves

What are the three types of tracts in white matter?

1. Tracts that connect various areas of cortex, within the same hemisphere

2. Tracts that carry impulses between left & right hemisphere

3. Tracts rear connect cortex to other parts of the brain or spinal cord

What is the corpus callosum?

• wide band of nerve fibres that lie underneath cerebrum at base of longitudinal fissure

How are the nerves in the corpus callosum structured?

• Cross from one hemisphere to another to allow wi sides of cerebrum to communicate with each other

What is the cerebellum?

• lies under rear part of cerebrum

• Second-largest part of brain

• Surface folded into series of parallel ridges

• Outer folded part of cerebellum is gray matter, inside is white matter that branches to all parts of cerebellum

What does the cerebellum control?

• posture, balance, fine coordination of voluntary muscle movement

• All functions take place below conscious level

• → impulses do not originate in cerebellum, so without we can still move, but movements would be spasmodic, jerky & uncontrollable

Where does the cerebellum receive sensory info from?

• inner ear for information about posture & balance

• Stretch receptors in skeletal muscles for info about length of muscles

What is the hypothalamus?

• lies in the muddle of brain

• Controls many bodily activities

• Mostly concerned with maintaining constant internal environment (homeostasis)

What are the functions of the hypothalamus?

1. Regulation of autonomic nervous system (heart rate, blood pressure, secretion of digestive juices etc)

2. Body temp

3. Food & water intake

4. Patterns of waking & sleeping

5. Contraction of urinalysis bladder

6. Emotional responses (fear, anger, aggression, pleasure & contetment)

7. Secretion of hormones & coordination of parts of endocrine system (acting through pituitary gland)

8. Regulates metabolism, growth, reproduction & responses to stress

What is the medulla oblongata?

• continuation of spinal cord

• 3cm long, extends from just above where spinal cord enters skull

• Many nerve fibres simply pass through medulla to or from other parts of brain

• → but medulla plays important role in automatically adjusting body functions

What does the medulla oblongata obtain?

• cardiac centre : regulates rate & force of heartbeat

• Respiratory centres : control rate & depth of breathing

• Vasomotor centre : regulates diameter of blood vessels

• Other centres regulate reflex of swallowing, sneezing, coughing & vomiting

What is the spinal cord?

• roughly cylindrical structure ~144cm long in adults

• Extends from foremen magnum, large opening at base of skulls to second lumbar vertebra (at waist level)

How is the spinal cord protected?

• enclosed in vertebral canal

• Inside ring of bones is 3 meningeal layers (outermost layer not joined to the bone)

• Space containing fat, connective tissue & blood vessels serve as padding around spinal cord

• → allows cord to bend when spine is bent

What does the inside of the spinal cord look like?

Grey matter at centre of spinal cord (nerve cell bodies unmyelinated nerve fibres)

Surrounded by white matter (myelinated fibres)

How is the grey matter shaped?

Letter H

In cross bar of H is small space called central canal (runs length of spinal cord & contains cerebrospinal fluid)

How is the white matter arranged?

In bundles known as ascending & descending tracts

What are ascending tracts?

Sensory axons that carry impulses upwards, towards the brain

What are descending tracts?

Contain motor axons that conduct impulses downwards, away from brain

What do the tracts tell about the spinal cord’s function?

Show spinal cord carries sensory impulses up to brain, and motor impulses down from brain

2. Integrate certain fast, automatic responses (reflexes)

What is the peripheral nervous system?

Takes messages from recents to CNS

Takes messages from CNS to muscles & glands

What is the PNS composed of?

Nerve fibres (carry info to and from CNS)

Groups of nerve cells (ganglia), lie outside spinal cord & brain

What are cranial nerves?

• 12 pairs of nerves (optic, auditory, etc) arise from brain

• Most are mixed nerves

• → contain first that carry impulses into brain as well as fibres that carry impulses away from brain

What are Spinal nerves?

• 31 pays of spinal nerves arise from spinal cord

• All iced nerves containing both sensory & motor fibres

• Each nerve joined to spinal cord by 2 roots

What are the two roots that join the nerve to the spinal cord?

Ventral root: contains axons of motor neurons that have their cell bodies in grey matter of spinal cord

Dorsal root: contains axons axons of sensory neurons that have their cell bodes in dorsal root ganglion (small swelling on dorsal root)

What is the afferent division of the PNS?

aka Sensory division

• carry impulses into CNS by sensory neurons

• → from receptors in skin & around muscles & joints

How is the afferent division further divided?

• Somatic sensory neurons : bring impulses from skin & muscles

• Visceral sensory neurons : bring impulses from internal organs

What is the efferent division of the PNS?

Aka Motor division

• has fibres that carry impulses away from CNS

• further divided

How is the efferent division subdivided?

Somatic division/ Somatic nervous system: takes impulses from CNS to skeletal muscles

Autonomic division/ Autonomic nervous system: carries impulses from CNS to heart muscle, involuntary muscles & glands. Further subdivided

What is the ANS further subdivided?

• Sympathetic NS

• Parasympathetic NS