Nervous system

Nervous system

• Nervous system consists of the brain, spinal cord, and nerves.

• Nervous tissue consists of neurons; whereas the brain and spinal cord contain all parts of neurons, nerves contain only axons.

Nervous tissue

dendrite

nucleus

cell body

axon

astrocyte

Oligodendrocyte

Microglia

Neurons

• Motor Neurons–Accept nerve impulses from the Central nervous

system (CNS)–Transmit them to muscles or glands

• Sensory Neurons –Accept impulses from sensory receptors–Transmit them to the CNS

• Interneurons–Convey nerve impulses between various parts of

the CNS

CNS & PNS

• Central nervous system = Brain + Spinal cord

• Peripheral nervous system = Cranial nerves + Spinal nerves (gather info from sensors and conduct decisions to effectors)

Nerves• Structures containing many long fibers with myelin

sheath (axons / dendrites)

• Nerves do not contain cell bodies

Brain

• Cerebrum

• Diencephalon

• Cerebellum

• Midbrain

• Pons

• Medulla

Brain stem

Cerebrum

• Cerebral CortexA thin but highly convoluted outer layer of gray matter

• 4 lobes:

frontal lobe; temporal lobe; parietal lobe; occipital lobe

White matter

The rest of cerebrum except cerebral cortex

• Responsible for higher mental capabilities

Diencephalon

A region encircling the 3rd ventricle Consists of hypothalamus + thalamus + pineal gland

Hypothalamus forms floor of the 3rd ventricle Thalamus located in the sides and roof of the 3rd ventricle Pineal gland secretes melatonin

Helps integrate mental functions, primitive emotion and sleep

Cerebellum

• Separated from the brain stem by the 4th ventricle

– Receives sensory input from the eyes, ears, joints, and muscles

– Sends motor impulses out the brain stem to the skeletal muscles

• Helps maintain balance and produce smooth movements

Brain stem• Contains the midbrain, the pons, and the medulla

oblongata

–Midbrain

• Acts as a relay station for tracts passing between

the cerebrum, and the spinal cord or cerebellum

– Pons

• Helps regulate breathing and head movements

–Medulla oblongata

• Contains reflex centers for vomiting, coughing, sneezing, hiccuping, and swallowing

Spinal cord• The center for many reflex actions (involuntary and

predictable response to a given stimulus)

• Contains white and butterfly-shaped gray matter

Spinal reflexes

• A reflex is an involuntary and predictable response to a given stimulus.

• The brain is not involved in formulating the response.

dorsal ventral

Experiment

• Dissecting sheep brain, observing structure of brain

• Observing prepared slides and learning the structure of spinal

• Spinal Reflexes page 432