Biopsychology

The nervous system –

Is a collection of nerves and cells, known as neurons, which transmit signals between different parts of the body. Our primary communication system and it has two main functions: to collect, process and respond to info from environment, and, coordinate working of organs. The nervous system has 2 components: CNS & PNS.

CNS –consists of the brain and spinal cord. Brain is the centre of all conscious awareness. Spinal cord passes messages to and from brain and connects nerves to PNS. It controls behaviour and regulates processes.

PNS – compromises of somatic and autonomic NS. The somatic is nerves carrying sensory signals over the body and nerves that carry messages from the brain to other areas and muscle movement. The autonomic governs vital bodily functions such as breathing, heart rate and digestion. It is divided into sympathetic and parasympathetic NS.  

Differences:

SNS -                                                                                                     ANS -

Sensory and motor paths                                                             only motor

Controls skeletal muscles and movement                             controls internal organs and glands

Carries commands from motor cortex                                    control centres are in the brain

Sympathetic NS – starts up in situations needing arousal and energy. Increased heart rate and breathing rate, pupil dilation and reduced gut activity. This prepares for fight or flight

Parasympathetic NS - when the body is trying to save energy. Opposite of the sympathetic, decreased hear rate, increased gut activity etc. this is the rest and digest state after the fight or flight stage.

Neurons carry impulses from place to place. They connect receptors to the CNS and one part of the NS to another e.g. brain and spinal cord. Carry impulses from NS to effector organs e.g. muscles or glands

When they are simulated they transmit electrical impluses.

Sensory neurons – carry sensory messages from PNS to CNS, towards the brain. These are from the senses. They have long dendrites and short axons.

Relay neurons – connect sensory to motor neurons. Once you have registered the information, relay neurons link with motor neurons allowing you to act. They have short dendrites and short axons

Motor neurons – connect the CNS to muscles and glands. They are concerned with generating movement, knee bending, arm movement. Carry messages away from brain, coordinating movement. They have short dendrites and long axons.

Excitatory neurotransmitters – trigger nerve impulses in receiving neuron and stimulate the brain. Inhibitory neurotransmitters – they inhibit nerve impulses to calm the brain and balance mood

Excitation – when neurotransmitter increases the positive charge of postsynaptic – increasing likelihood that neuron will fire and pass the next electrical impulse e.g. adrenaline

Inhibition – when NTM makes the postsynaptic more negative, decreasing likelihood the neuron will fire e.g. GABA

• Neuron resting (negative charge)

• Neuron activated by stimulus (positive charge)

• this is called action potential of the neuron

• this creates an electrical impulse that travels down the axon to synapse
• When impulse reaches the end of the neuron, it triggers release of neurotransmitters from synaptic vesicle sacs.
• Chemically transmitted to next neuron via neurotransmitters

• The endocrine system works with the nervous system to regulate the physiological processes of the human body, it controls vital functions in the body.

• Various glands in the body produce hormones, the glands secret the hormones into the bloodstream where they are slowly transported around the body, they affect any cell that has a receptor for that particular hormone (target cells).

• The endocrine system is controlled by the hypothalamus.

The Pituitary Gland

Located in the brain, it is often called the ‘master gland’, that controls the release of hormones from all other endocrine glands.

It has two parts that release different hormones to target different parts of the body:

The Anterior pituitary                                                     The Posterior pituitary

Pituitary – master gland, controls all other endocrine glands

Thyroid – cells in the heart, increases metabolic rate, affects growth

Thymus – immune system

Adrenal – produces adrenaline (fight or flight)

Pancreas – produce insulin

Ovaries – facilitate the release of oestrogen and progesterone

Testes – facilitate the release of testosterone

• The endocrine system and autonomic NS work in parallel with on another e.g. during a stressful situation.

Adrenal Glands

Sit on top of the kidneys. Hormones released by the adrenal cortex are necessary for life, those from the adrenal medulla are not.

Adrenal cortex – produces cortisol which regulates or supports bodily functions like cardiovascular systems. Cortisol production is increased in stress. If its level is low, the person has low blood pressure etc and inability to deal with stress.

Adrenal medulla – releases adrenaline and noradrenaline in preparation for fight or flight. Adrenaline helps the body respond to a stressful situation by increasing heart rate and blood flow. Noradrenaline constricts the blood vessels, causing blood pressure to increase.

If there are serious stressors, it triggers an alarm reaction that prepares your body for action. Stress hormones and action of the sympathetic nervous system prepare your body for vigorous muscular activity and the parasympathetic nervous system returns the body to its normal state.  

The Stress Response

1.       When a stressor is perceived, the ANS changes to the sympathetic state

2.       The pituitary gland releases ACTH

3.       ACTH has an effect on the cells of the adrenal glands causing them to release adrenaline into the bloodstream. Adrenaline causes physiological changes needed for the fight or flight.

4.       Once the threat has passed that Parasympathetic NS returns the body to Rest & Digest state, working in opposition to the sympathetic.

Amygdala (associated with emotions)   >   Hypothalamus which activates   >   Sympathetic branch of ANS sending distress signals to   >   Adrenal medulla which secrets   >   Adrenaline which leads to   >   fight or flight response

Our sympathetic NS immediately prepares us for action, designed to deal with short-lived stress by channelling resources into areas of the body where they are needed.

One the threat has passed the parasympathetic NS returns the body to its resting state and works in opposition to the sympathetic division – rest and digest.