THE NERVOUS SYSTEM

The Nervous System

Complex network of neurons that regulates bodily processes

Has two major portions that functions as an integrated whole:1) The Central Nervous System2) The Peripheral Nervous System

Central Nervous System

CNS – consists of the brain and the spinal cord

Spinal Cord 2 Major Functions: i) Carries sensory

information from receptors throughout the body to the brain AND conducts information from the brain to muscles and glands.

ii) Plays a key role in various reflexes – e.g. the hammer tap, hot stove! (behaviour produced without help from the brain)

Damage to CNS

Originally thought be permanent Scientists have since been able to implant

nerve fibers from outside the spinal cord onto the damaged area to allow the damaged spinal nerves to grow through the implants.

Also know now that the brain can change itself by adapting neurons to serve new functions when old neurons die or are damaged.

PERIPHERAL SYSTEM Made up of all the nerves and

neurons not contained in the brain and spinal cord.

Allows the brain and spinal cord to communicate with the sensory systems of the eyes, ears, skin, and mouth and allows the brain and spinal cord to control the muscles and glands of the body.

PNS divided into two major systems: somatic and autonomic

The Somatic Nervous System Senses CNS and from CNS muscles Only voluntary muscles are controlled by

the SNS (e.g. walking, raising hands, smelling flower, seeing art)

Nerves coming from the senses to the spinal cord and the brain are called sensory pathways (made up of sensory neurons)

Nerves carrying messages to skeletal muscles are called motor pathways (made up of motor neurons)

AUTONOMIC NERVOUS SYSTEM Autonomic suggests automatic! Controls organs, glands, and involuntary

muscles – parts of the body that keep us alive (heart, lungs, blood vessels and glands)

Transmits info to and from the CNS = automatic links from CNS with vital internal organs.

Operates continuously, involuntarily and without awareness.

Divided into two systems: sympathetic division and parasympathetic division.

Sympathetic

Fight-or-flight system – responsible for reacting to stressful events and bodily arousal in emergency situations!

To increase energy, sugar is released into the bloodstream. To hasten distribution of blood to muscles, heart beats faster. Facilitates survival in the face of danger.

Located on the middle of the spinal column – running from near the top of the ribcage to the waist area.

Parasympathetic

After the danger passes, the parasympathetic division of the ANS takes over.

Restores us to a calmer state. Reverses changes mage by the

sympathetic system. Responds more slowly than sympathetic

– can take 20 – 30 min to calm down.

Major Functions of the ANS

Body Organ Sympathetic Division Parasympathetic Division

Pupil of the eye

Heart

Stomach

Intestines

Adrenal gland

Blood vessels in the skin

Bladder

Dilates

Rapid, accelerates

Inhibits activity

Inactive

Secretes adrenalin and noradrenaline

Constricts

Relaxes

Constricts

Slows

Stimulates activity

Active

No intervention

Dilate

Contracts

Schematic diagram of the NS

Nervous System (NS)

Central NS Peripheral NS

Brain Spinal Cord Somatic NS(Voluntary)

Autonomic NS(Involuntary)

Sympathetic NS(Arousing)

Parasympathetic NS

(Calming)