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The Nervous SystemBrain Review, Nerve & Spinal Cord Anatomy

The Lobes

Frontal Lobe Area around your forehead

Involved in purposeful acts like judgment, creativity, problem solving, and planning.

Parietal Lobe Top back area of the brain

Processes higher sensory and language functions

Temporal Lobe Left and right side above and around the ears

Primarily responsible for hearing, memory, meaning, and language.

Some overlap in functions of the lobes.

Occipital Lobe Back of the brain

Primarily responsible for vision

The Limbic System

Emotional Center

Hypothalamus Hunger, thirst, body temperature, pleasure; regulates pituitary gland (hormones)

Pituitary “Master Gland”

Stimulates other glands to produce hormones

Amygdala Aggression (fight) and fear (flight)

Hippocampus Memory processing

Facts about the Brain

Weighs approximately 3 pounds Mostly water - 78%

Fat - 10%

Protein - 8%

Soft enough to cut with a butter knife

Grapefruit-sized organ

Outside of the brainConvolutions or folds

Wrinkles are part of the cerebral cortex

Folds allow maximum surface area

Brain

There are two types of brain cells:

Glial cells

Neurons

Brain matter has two colors

Grey Matter

White Matter

Glial Cells

Function:To surround neurons and hold them in place

To supply nutrients and oxygen to neurons

To insulate one neuron from another

To destroy pathogens and remove dead neurons.

90% of the brain cells

Less known about glia cells

No cell body

Neurons

Neurons (Greek word meaning bowstring) 100 billion neurons in human brain

Neurons essential to performing the brain's work

Consist of a compact cell body, dendrites, and axons

Neurons

Neurons (brain cells) make connections between

different parts of the brain.

Information is carried inside a neuron by electrical

pulses and transmitted across the synaptic gap

from one neuron to another by chemicals called

neurotransmitters.

Learning is a critical function of neurons.

Dendrites and Axons

Dendritic branching helps make connections between cells.

As cells connect with other cells, synapses occurs.

New synapses appear after learning.

Repeating earlier learning makes neural pathways more efficient through myelination (fatty substances formed around axons)

Grey Matter

Consists mostly of cell

bodies of Neurons

Makes up about 40% of

the brain content

The processing taking

place in this area consists

mostly of sensory

information; speech,

hearing, feelings, vision,

and memory.

White Matter

Consists of nerve fibers or

axons of neurons.

The white color is due to

the myelin sheath.

Allows communication to

and from grey matter areas

and between the brain and

body.

Controls automatic

functions (heart rate,

breathing, temperature

regulation, etc.)

Meninges

3 membranes that cover and protect the brain

and spinal cord

Dura mater – outer layer

Arachnoid membrane – middle, delicate layer

Pia mater – attached to the brain and contains

blood vessels that nourish the nerve tissue

Spinal Cord

Spinal cord

Continues down from the medulla oblongata

Surrounded and protected by vertebrae

Responsible for many reflex actions and

carrying afferent and efferent nerves

Spinal nerves carry messages to and from the spinal cord and are mixed nerves (both afferent and efferent)

Cross Section of Spinal Cord

11-7

Spinal Tract• groups of axons with cell bodies in the same area that are headed to the samedestination

Generalizations1. Most cross from one side of the

spinal cord to the other (decussate)

2. contain 2 or more neurons

3. Somatotopy – the locations of the tracts in the spinal cord reflects the mapping of the body

4. All tracts are paired with one on each side of the spinal cord

Ascending Pathways

Usually contain 3 successive neurons

First Order Neurons – body in ganglion (dorsal or cranial)

-- get impulses from skin and proprioceptors in the

spinal cord to the brain stem

Second Order Neurons – body in dorsal horn or medullary

nuclei

-- transmit impulse to thalamus or cerebellum

Third Order Neurons – body in thalamus

--send info to cortex

Sensory

Descending TractsMotor

Direct Pathway – originate in cortex

• No synapses until they reach the spinal cord

• Interacts with interneurons or in the ventral horn

• Activates skeletal muscle to do skilled movements (writing)

Indirect Pathway (multineuronal)

• all other descending tracts

• usually rely of reflexes

• regulate

•Axial muscle for balance and posture

•Muscle controlling course limb movement

•Head, neck, and eye movement

Reflex Pathways

Receptors in the skin send

signals through sensory

neurons.

Signals travel to the spinal

cord and up to the brain.

Signals from the brain

travel back down the spinal

cord.

Motor neurons from the

spinal cord send signals to

muscles to move.