Anatomy of the Nervous and Endocrine Systems: Neurons, Glands, and Hormones, Lecture notes of Psychology

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AS PSYCHOLOGY REVISION

BIOPSYCHOLOGY

3.2.1 Approaches in Psychology

Specification

3.2.1.1 Biopsychology

• The divisions of the nervous system: central and

peripheral (somatic and autonomic).

• The structure and function of sensory, relay and

motor neurons. The process of synaptic

transmission, including reference to

neurotransmitters, excitation and inhibition.

• The function of the endocrine system: glands and

hormones.

• The fight or flight response including the role of

adrenaline.

CENTRAL AND PERIPHERAL NERVOUS SYSTEMS

THE CEREBRUM

CEREBRUM – This is the largest part of the brain divided into 4 other parts

• FRONTAL LOBES – functions such as speech, thought and learning
• PARIETAL LOBES – sensory information (touch, pain, temperature)
• TEMPORAL LOBES – hearing and memory
• OCCIPITAL LOBES – visual information
• The cerebrum is split down the

middle into two CEREBRAL

HEMISPHERES

• Each hemisphere is specialised

for particular behaviours and the

two halves communicate with

each other through the CORPUS

CALLOSUM

THE CEREBELLUM

• This is found underneath the back of the cerebrum
• It controls a person’s MOTOR skills and balance, coordinating the muscles to cause precise movements
• Speech and motor problems and epilepsy are caused if there are abnormalities in the cerebellum

CENTRAL AND PERIPHERAL NERVOUS SYSTEMS

THE DIENCEPHALON

• This is found beneath the

cerebrum and on top of the brain

stem

• There are two important

structures found here:

• The THALAMUS
  • This is a relay station for nerve impulses from the senses, steering them to the appropriate part of the brain to be processed
• The HYPOTHALAMUS
  • Functions include the regulation of body temperature, hunger and thirst
  • This is a link between the ENDOCRINE SYSTEM (glands and hormones) and the nervous system, controlling the release of hormones from the pituitary gland

CENTRAL AND PERIPHERAL NERVOUS SYSTEMS

CENTRAL NERVOUS SYSTEM

(CNS)

THE PERIPHERAL NERVOUS

SYSTEM

• This is made up of all the

nerves outside of the CNS

• Its function is to relay nerve

impulses from the CNS to

the rest of the body and

from the body back to the

CNS

• There are two sections of

the Peripheral Nervous

System:

• SOMATIC NERVOUS SYSTEM
• AUTONOMIC NERVOUS

SYSTEM (ANS)

The brain is the centre of awareness. It is divided in two hemispheres. The cortex is more developed in humans than in all other animals.

The spinal cord is an extension of the brain. It transports messages to and from the brain to the peripheral nervous system. It is also responsible for reflexes.

CENTRAL AND PERIPHERAL NERVOUS SYSTEMS

THE PERIPHERAL NERVOUS SYSTEM

THE SOMATIC NERVOUS SYSTEM

• This is made up of 12 pairs of cranial nerves (nerves that come directly from the underside of the brain) and 31 pairs of spinal nerves (nerves that come directly from the spinal cord)
• These nerves have both SENSORY NEURONS and MOTOR NEURONS
• Sensory Neurons relay messages TO the CNS
• Motor Neurons relay information FROM the CNS to other areas of the body
• The somatic system is also involved in reflex actions without the involvement of the CNS , which allows for the reflex to occur very quickly

THE PERIPHERAL NERVOUS SYSTEM

AUTONOMIC NERVOUS SYSTEM (ANS)

• Involuntary actions are regulated by the ANS (e.g. carrying out some actions without conscious awareness like. digesting food, etc)
• The ANS is essential because vital body functions would not work as efficiently If we had to think about them
• The ANS is split into THE PARASYMPATHETIC NERVOUS SYSTEM and THE SYMPATHETIC NERVOUS SYSTEM - These sections of the ANS regulate the same organs but have the opposite effects - This is due to the neurotransmitters associated with each division - Generally the sympathetic system uses NORADRENALINE (also known as NOREPINEPHRINE) which has a stimulating effect and the parasympathetic system uses ACETYLCHOLINE which has inhibiting effects

THE OPPOSING ACTIONS OF THE SYMPATHETIC AND THE

PARASYMPATHETIC NERVOUS SYSTEM

ORGAN SYMPATHETIC NERVOUS SYSTEM PARASYMPATHETIC NERVOUS

SYSTEM

GUT Slows digestion Increases digestion

SALIVARY

GLANDS

Inhibits saliva production Increases saliva production

HEART Increases heart rate Decreases heart rate

LIVER Stimulates glucose production Stimulates bile production

BLADDER Stimulates urination (relaxes the

bladder)

Inhibits urination (contracting

bladder)

EYE Dilates pupils Constricts pupils

LUNGS Dilates bronchi Constricts bronchi

HUMAN

NERVOUS

SYSTEM

Peripheral nervous system (PNS)

Central nervous system (CNS)

Autonomic nervous system

Somatic nervous system

Brain Spinal cord

Sympathetic nervous system

Parasympathetic nervous system

The major sub-divisions of the human nervous system

3.2.1 Approaches in Psychology

Specification

3.2.1.1 Biopsychology

• The divisions of the nervous system: central and

peripheral (somatic and autonomic).

• The structure and function of sensory, relay and

motor neurons. The process of synaptic

transmission, including reference to

neurotransmitters, excitation and inhibition.

• The function of the endocrine system: glands and

hormones.

• The fight or flight response including the role of

adrenaline.

• Neurons carry neural information throughout the body
  • They are either sensory neurons, relay neurons or motor neurons
• Neurons consist of a cell body, dendrites and an axon
• Dendrites connect to the cell body (which controls the neuron)
• Impulses are carried along the axon from the cell body, where

it terminates at the axon terminal (end)

• In many nerves they have an insulating layer that covers the

axon , called the MYELIN SHEATH

• This allows nerve transmitters to transmit more rapidly along the axon
• If the myelin sheath is damaged then the message slows down
• Neurons can be a few millimetres up to one meter

STRUCTURE AND FUNCTION OF

NEURONS

THREE TYPES OF NEURONS

SENSORY NEURONS

• These carry nerve impulses FROM sensory receptors (e.g. receptors for vision, touch, taste, etc.) TO the spinal cord (found in eyes, ears, tongue and skin
• They convert this information into neural impulses
• When these impulses reach the brain they are translated into sensations of visual input, heat, pain etc. so the appropriate reaction can be made
• Some neurons do not travel to

the brain, they terminate at the spinal cord

• This allows reflex actions to occur quickly without the delay of sending impulses to the brain

RELAY NEURONS

• Most neurons lie somewhere between the sensory input and the motor output
• They allow sensory and motor neurons to communicate with each other
• The relay neurons lie wholly within the brain and spinal cord

MOTOR NEURONS

• These neurons are located in the central nervous system (CNS) that project their axons outside the CNS and directly or indirectly control muscles
• They form synapses with muscles and control their contractions
• When motor neurons are stimulated they release neurotransmitters that bind to receptors on the muscle and trigger a response which leads to muscle movement
• When the axon of a motor neuron fires, the muscle with which it has formed a synapse with contracts
• The strength of the muscle contraction depends on the rate of firing of the axons or motor neurons that control it
• Muscle relaxation is caused by the inhibition of the motor neuron

SYNAPTIC TRANSMISSION

ACTION POTENTIAL

• Neurons must transmit

information both within the

neuron and from one neuron to

the next

• The dendrites of neurons receive

information from sensory

receptors or other neurons

• This information is then passed

down to the cell body and to the

axon

• Once the information has arrived

at the axon, it travels down its

length in the form of an

electrical signa l known as an

ACTION POTENTIAL

SYNAPTIC TRANSMISSION

• Once an action potential has

arrived at the terminal (end) of

the axon, it needs to be

transferred to another neuron

or tissue

• So it must cross the gap

between the presynaptic neuron

(the one sending the

information) and the

postsynaptic neuron (the one

receiving the information)

• This area is known as the SYNAPSE and includes the end of the presynaptic neuron, the membrane of the postsynaptic neuron and the gap between them
• This gap is known as the SYNAPTIC GAP

SYNAPTIC TRANSMISSION

• The whole process of SYNAPTIC

TRANSMISSION only takes a fraction of a second

• The effects of the transmission are

terminated at most synapses by a process called RE-UPTAKE

• The neurotransmitter is taken up

again by the presynaptic neuron where it is stored and made available for later release (a recycling programme)

• How quickly this happens

determines how prolonged its

effects will be

• I.e. if it is taken back quickly its effects on the postsynaptic neuron are short-lived and vice-versa - Some antidepressant drugs prolong the action of neurotransmitter by inhibiting the re-uptake process , leaving the neurotransmitter in the synapse for longer - Neurotransmitters can also be “turned off” after they have stimulated the postsynaptic neuron - This takes place through the action of enzymes produced in the body, which make the neurotransmitters ineffective

EXCITATORY AND INHIBITORY NEUROTRANSMITTERS

• Neurotransmitters can be classified as either excitatory or inhibitory in their action
• Excitatory neurotransmitters (e.g. acetylcholine and noradrenaline) are the nervous system’s “on switches”
• These increase the likelihood that an excitatory signal is sent to the postsynaptic cell , which is then more likely to fire
• Inhibitory neurotransmitters (e.g. serotonin and GABA) are the nervous system’s “off switches” in that they decrease the likelihood of that neuron firing
• Inhibitory transmitters are generally responsible for calming the mind and body, inducing sleep and filtering out unnecessary excitatory signals - An excitatory neurotransmitter

binding with a postsynaptic

receptor causes an electrical change in the membrane of

that cell, resulting in an

excitatory postsynaptic

potential (EPSP)

• Meaning that the postsynaptic cell is more likely to fire
• An inhibitory neurotransmitter

binding with a postsynaptic

receptor results in an inhibitory

postsynaptic potential (IPSP)

• Making it less likely that the cell will fire