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Biology 3201 Nervous

System #2- Anatomy

Components of a Nervous

System

In any nervous system, there are 4 main components:

(1) sensors: gather information from the external environment (sense organs)

(2) conductors: carry information from sensors to modulators or from modulators to effectors (nerves)

(3) modulators: interpret sensory information and send information to effectors (brain, spinal cord)

(4) effectors: part of the body that responds because

of information from a modulator (muscles, glands)

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Two main components of the human nervous system:

(1) central nervous system (CNS): the brain and spinal cord

(2) peripheral nervous system (PNS): the nerves that enter and leave the brain and spinal cord .

The CNS

receives sensory information and initiates control

protected by several things:

(1) skull – hard casing that protects the brain

(2) vertebrae – protects spinal cord

(3) meninges – three protective membranes surrounding the brain and spinal cord. They are filled with cerebrospinal fluid to help cushion.

(4) Ventricles (cavities) in the brain which are filled with cerebrospinal fluid

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CNS continued...

→ grey matter: brownish-grey nerve

tissue consisting of mainly cell bodies within the brain and spinal cord

→ white matter: the white nerve tissue of

the brain and spinal cord, consisting of mostly myelinated neurons

PNS

→ two parts:

(1) autonomic nervous system: the part of the nervous system that relays information to the internal organs that are not under the conscious control of the individual. This system is made up of the sympathetic and the parasympathetic nervous systems.

sympathetic: speeds up muscle activity and activates in times of stress; “fight or flight response”

• ex. Increases heart rate, breathing rate, nervousness

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PNS

parasympathetic: the network of nerves that counteract the sympathetic nervous system to slow down heart rate and relax muscles

(2) somatic nervous system: the part of the nervous system that relays information to and from skin and skeletal muscles that are under conscious control of the individual

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The Brain see Fig. 12.11, p. 399

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See graphic pp 400 ****

See graphic pp 400 ****

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Parts of the Brain

1. Cerebrum

→ largest part of the brain; cerebral

cortex folded to increase surface area

→ responsible for complex behavior and

intelligence; also interprets sensory inputs and initiates motor response

quickly

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Cerebrum

→ cerebral cortex divided into 4 lobes:

(1) frontal lobe – contains primary motor area, premotor area, Bronca’s area (motor speech), and pre-frontal area (association)

(2) temporal lobe – located at sides of head

- contains auditory association area, primary auditory area, and sensory speech (Wernche’s area)

(3) parietal lobe – located near top of brain

- contains primary somatosensory area, somatosensory association area and primary taste area

(4) occipital lobe – located at back of cerebrum

- contains primary visual area and visual association area

Cerebrum

→ cerebral cortex divided into two

hemispheres, right and left. The cortex consists of grey matter and the two hemispheres are connected by a structure called the corpus callosum, a layer of white matter which transmits between the two hemispheres really

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Parts of the Brain cont...

2. Cerebellum

→ the part of brain that is responsible for muscle coordination

→ contains 50% of the brain’s neurons but only takes up 10% of the space

3. Midbrain

→ a short segment of the brainstem (midbrain, pons and medulla oblongata) between the cerebellum and pons; particularly involved in sight and hearing

Parts of the brain

4. Pons

→ contains bundles of axons traveling between the cerebellum and the rest of the CNS

→ functions with the medulla oblongata to regulate breathing rate and has reflex centers involved in head movement

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Parts of the Brain

5. Medulla Oblongata → attaches to the

spinal cord at the base of the brain

→ involved in several important processes:

- controlling heart rate - vomiting

- adjusting blood pressure - hiccupping

- controlling breathing - swallowing

6. Thalamus

→ sensory relay center of the brain that governs the flow of information from all other parts of the nervous system

Parts of the Brain

7. Hypothalamus

→ The part of the brain that acts as the main control centre for the autonomic nervous system, reestablishes homeostasis, and controls the endocrine hormone system

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Trends in evolution of a

complex brain

Ratio of brain to body mass increases

Increase in the relative size of the cerebrum

Compared to other primates newborn humans have a very large brain

contains about 100 billion neurons

2% of body weight, but contains 15% of blood supply and consumes 20% of the body’s oxygen and glucose.

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The Spinal Cord

continues from the medulla oblongata

protected by vertebrae, meninges and cerebrospinal fluid

The Spinal cord

outer part is white matter (axons) while the inner part is grey matter (cell bodies).

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