L1 Nervous system organisation

1. Biological Psychology

Nervous system (NS)

Electrical wiring, communicate internally, sending and receiving

Divided into the CNS and PNS

Central nervous system (CNS)

Consisting of the brain and spinal cord

Peripheral nervous system (PNS)

Made up of the nerve tissue outside of the CNS that connects the CNS with receptors, muscles and glands

Brain

Organ made up of nerve tissue that controls body functioning

Spinal cord

A cylindrical structure that runs down the bony vertebral column and connects the brain to the PNS

Sensory neurons

Transmit nerve impulses from receptors to the CNS

Motor neurons

Transmit nerve impulses from CNS to effectors (muscles or glands)

Neurons

Microscopic nerve cells

Interneurons

Found within the spinal cord. Transmit nerve impulses from sensory neurons to motor neurons.

PNS

• Neurons are nerve cells

• Neurons are arranged into nerves fibres

• Nerve fibres are bundled into nerves

• Nerves of the PNS can contain: just sensory neurons, just motor neurons, or mix

Cranial nerves of the PNS

• Motor nerve contains motor neurons which send information from the CNS to effectors

• Sensory nerve contains sensory neurons which transmit information from receptors to the CNS

Spinal nerves of the PNS

Each spinal nerve consists of both motor and sensory fibres

Somatic NS

Nerves in the somatic nervous system contains motor neurons which relay nerve impulses from the CNS to stimulate voluntary skeletal muscle.

Transmit sensory information from effectors to the CNS via sensory neurons

Autonomic NS

Contains motor neurons which relay messages from the CNS to stimulate involuntary muscle contraction

Regulates the function of internal involuntary organs such as:

• Heart

• Digestive tract

• Pupils

• Salivary glands

etc.

Autonomic NS vs Somatic NS

Autonomic:

• Involuntary muscles and glands

• Regulation of internal environment

• Unconscious/involuntary

Somatic:

• Voluntary skeletal muslces

• Responding to external environment

• Conscious/voluntary

Division of the autonomic NS

Divides into the sympathetic NS and the parasympathetic NS

Excitation

Stress response

Inhibition

Normal functioning or a relaxed state

Fight or flight response

Evoluntionary adaptations to increase chances of survival in threatening situations

What happens during the fight or flight response?

An autonomic physiological reaction activated by the sympathetic nervous system

Sympathetic F/F R: heart

Increased heart rate:

• increase in blood flow to cells

• increase availability of oxygen and glucose for energy

Sympathetic F/F R: circulation

Dilation of blood vessels serving skeletal muscles:

• increased availabillity of oxygen and glucose in skeletal muscles

Constriction of blood vessels serving digestive organs:

• blood shunted to skeletal muscles and brain to fight or fly

Sympathetic F/F R: lungs

Dilation of bronchi, increased breathing rate:

• increased availability of oxygen in blood

Sympathetic F/F R: liver

Increased conversion of stored energy to increased blood glucose:

• increased availability of glucose in skeletal muscle and brain cells

Sympathetic F/F R: skin

Skin becomes pale as blood flow to skin is reduced, sweat glands increase sweat production:

• increased blood flow to skeletal muscles and away from non-essential parts of the body

• sweat cools the body

Sympathetic F/F R: eyes

Dilation of pupils:

• allows more light so that visual acuity is improved to scan nearby surroundings

Organs involed in the parasympathetic NS

• Eyes: constrict pupils

• Salivary glands: stimulates salivation

• Heart: slows heartbeat

• Lungs: constrict bronchi

• Stomach: stimulates digestion

• Liver: stimulates bile release

• Intestines: stimulate peristalsis and secretion

• Bladder: contracts bladder

Organs involed in the sympathetic NS

• Eyes: dilate pupils

• Salivary glands: inhibit salivation

• Heart: accelerates heartbeat

• Lungs: dilate bronchi

• Stomach: inhibits digestion

• Liver: stimulates glucose release

• Intestines: inhibits peristalsis and secretion

• Kidneys: stimulate epinephrine and norepinephrine release

• Bladder: relaxes bladder