Coordination of the human body

• The endocrine and the nervous system function together to maintain a homeostatic state within the body.

• The nervous system transmits nervous impulses, whereas the endocrine system utilises the blood as a transport medium.

• Both systems share a common feature in the release of chemical substances as a means of communication between cells.

Differences between the systemsNervous Chemical

Information passes as electrical impulses along axons, across synapses.

Information passes as a chemical substance through the bloodstream.

Rapid transmission Slow transmission

Response immediate Response usually slow

Response short-lived Response long lasting

Response very exact Response usually widespread

The Nervous System

Organisation of the nervous system

Vertebrate nervous system

Central Nervous System Peripheral nervous system

Brain Spinal Cord Visceral nervous Somatic Nervous system (autonomic) system (voluntary)

Sympathetic Parasympathetic nervous system nervous system

Spinal Nerves Spinal Nerves Cranial Nerves Spinal Nerves Cranial Nerves only

The CNS

The CNS is composed of the brain and spinal cord.

It is covered by three membranes.

The function of the CNS involves the coordination, integration and control of most nervous activities and it works in conjunction with the peripheral nervous system.

The Peripheral Nervous System

• The peripheral nervous system consists of nerves that arise in the spinal cord and go to your arms, legs etc

Sympathetic / ParasympatheticThe sympathetic and the parasympathetic nervous system are parts of what is commonly called the autonomic nervous system. (Autonomic = can not be controlled by the mind).

The sympathetic nervous system has an active "pushing" function, the parasympathetic has mainly a relaxing function.

The autonomic nervous system is most important in two situations: emergency situations that cause stress and require us to "fight" or take "flight", and nonemergency situations that allow us to "rest" and "digest".

NeuronesNerves are cells that are capable of transmitting electical impulses.

Neurones that conduct impulses towards the CNS are called afferent neurons.

Neurones that conduct impulses away from the CNS are called efferent neurones.

Each neurone has a cell body, which contains a nucleus, an axon, which is insulated by a myelin sheath and nerve endings. Present on the cell body are dendrites and they conduct impulses towards the cell body.

Sense Organs Sight

Taste

Hearing

Smell

Touch

Effectors

• An effector is a differentiated structure, such as a cell, organ or organ system, performing a specific reaction relative to the environment in response to a stimulus from the nervous system.

• The most important effectors are those involved in movement and secretion.

The Reflex Arc

A reflex action is one that does not involve the brain.

A stimulus is detected by a receptor cell (in this case pressure sensors in the skin) the impulse is then carried along the sensory neurone to the spinal cord. The response is then coordinated. The impulse is carried by the motor neurone to the effector cell or organ, which will carry out the response.

SynapsesThe synapse is a small gap separating neurons. The synapse consists of: •a presynaptic ending that contains neurotransmitters, mitochondria and other cell organelles, •a postsynaptic ending that contains receptor sites for neurotransmitters and, •a synaptic cleft or space between the presynaptic and postsynaptic endings. It is about 20nm wide.

1. At the end of the pre-synaptic neurone there are voltage-gated calcium channels. When an action potential reaches the synapse these channels open, causing calcium ions to flow into the cell.2.These calcium ions cause the synaptic vesicles to fuse with the cell membrane, releasing their contents (the neurotransmitter chemicals) by exocytosis.3.The neurotransmitters diffuse across the synaptic cleft.4.The neurotransmitter binds to the neuroreceptors in the post-synaptic membrane, causing the channels to open. In the example shown these are sodium channels, so sodium ions flow in.5.This causes a depolarisation of the post-synaptic cell membrane, which may initiate an action potential, if the threshold is reached.6.The neurotransmitter is broken down by a specific enzyme in the synaptic cleft; for example the enzyme acetylcholinesterase breaks down the neurotransmitter acetylcholine. The breakdown products are absorbed by the pre-synaptic neurone by endocytosis and used to re-synthesise more neurotransmitter, using energy from the mitochondria. This stops the synapse being permanently on.

EEGAn electroencephalogram (EEG) is a test that measures and records the electrical activity of your brain. Special sensors are attached to your head and hooked by wires to a computer. The computer records your brain's electrical activity on the screen or on paper as wavy lines.

An EEG may be done toDiagnose epilepsyCheck for problems with loss of consciousnessFind out if a person who is in a coma is brain-dead. Study sleep disordersWatch brain activity while a person is receiving general anaesthesia during brain surgery.Help find out if a person has a physical problem

The endocrine system

• The endocrine is a complex system involving glands and hormones.

• It utilises the blood as a transport system.

Glands

• A gland is a structure secreting a specific chemical substance. There are two types in the body:– Endocrine glands – these have no ducts and the

hormones pass directly into the blood stream.– Exocrine glands – these have special ducts that

transport their secretions to the site of action.

Organisation of the endocrine system

The Pituitary Gland

Hypothalamus

• Monitors hormone levels in the blood.

• Passes information to the pituitary gland.

Thyroid & Parathyroid

The thyroid gland is the largest gland in the human body and is responsible for making T3 (triiodothyronine) and T4 (thyroxine) These hormones are responsible for the control of metabolism.

There are 4 parathyroid glands situated just behind the thyroid. They are involved in the control of calcium in the blood.

Pancreas

• The pancreas has two important jobs in the body. The first is to produce the pancreatic digestive juices. The second is to produce insulin and other hormones to do with digestion.

Adrenal • There are two adrenal glands. One sits on the top of each

kidney. The adrenal glands produce a number of vital hormones essential for survival.

• There are two parts of the adrenal glands. The inner part is known as the medulla, and the outer part (of the gland) is called the cortex.

• The adrenal cortex produces different types of hormones which are known collectively as steroids. They regulate different mechanisms within the body.

• The adrenal medulla produces the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine).

Pineal

• The pineal gland is found at the back of the brain. The function of the pineal gland is to produce the hormone melatonin. Melatonin is involved in regulating the body’s 'internal clock', controlling when we sleep and when we wake.

Gonads• The gonads are the organs that make gametes.• In the males it is the testes and in females it is the ovary.• Gonadal hormones induce growth of and maintain the cyclical

function of the reproductive tracts, accessory sex glands, and copulatory or ovipository organs.

• They provide for the storage, nutrition, and transport of gametes; the secretion of necessary substances onto the surface of gametes; and the ultimate extrusion of sperm, eggs, or the products of conception.

• In mammals, therefore, they prepare the vagina for copulation and the uterus for implantation of eggs; in addition, gonadal hormones maintain pregnancy until birth or until placental hormones can take over their function.

Some Endocrine glands and their hormones

Gland Hormone

Pituitary gland

Prolactin, FSH, LH, thyroid stimulating (TSH), adrenocortictrophic (ACTH) growth hormone

Thyroid Triidothyronine, thyroxine, calcitonin

Adrenal medulla

Adrenaline

Kidney Renin

Ovarian follicle

Oestrogen, progesterone

Hormomes

• Most hormones belong to one of three groups.– Amines – adreneline & thryoxine– Peptides & proteins – insulin and glucagon– Steroids – oestrogen, testosterone and

corticosteroids.

What do hormones do?

• Hormones may promote actions or they might have an inhibitory effect.

• They affect one specific organ, known as the target organ, or they have a more widespread, diffuse effects involving several organs. For example adrenaline that affects the heart, blood vessels and other glands.

Responding to stimuli

• Hormones will respond to three stimuli.1. The presence, or change in concentration of a

specific substance in the blood.2. The presence, or change in concentration of

another hormone in the blood.3. Nervous stimulation involving neurones of the

autonomic system.

Negative feedback

• Hormones are secreted in response, or the change in concentration of other substances or hormones.

• They are under the control of a feedback mechanism and in most cases negative feedback operates.

Negative Feedback

• When a substance or a change in concentration is detected a response is triggered that brings the level of substance back to normal.

Control of blood glucose by negative feedback

Normal level of glucose in blood

Insulin released from pancreas

Insulin production stops glucagon

secreted.

Level returns to normal

increasedecrease

Glycogen to glucose

Glucose to glycogen

Problems with the endocrine system

• Malfunctioning of the endocrine system can have some devastating effects on the body.

Growth Hormone Deficiency

• Pituitary dwarfism is caused by the pituitary gland failing to produce enough growth hormone.

Cushings• An endocrine disease that is caused due to excessive

production of cortisol and is also referred to as 'hypercortisolism'.

• Cortisol is a hormone in the body, secreted by the adrenal glands and involved in the following functions and more: – Proper glucose metabolism – Regulation of blood pressure – Insulin release for blood sugar maintanence – Immune function – Inflammatory response

• Typically persons suffering from Cushing's syndrome experience upper body obesity as also severe fatigue, weak muscles and fragile bones.

Diabetes• Diabetes mellitus is a condition where the amount of glucose

in the blood is too high because the body cannot use it properly.

• Insulin is vital for life. It is a hormone produced by the pancreas and helps the glucose to enter the cells where it is used as fuel for energy so we can work, play and generally live our lives.

• Type 1 diabetes develops if the body is unable to produce any insulin.

• Type 2 diabetes develops when the body can still make some insulin, but not enough, or when the insulin that is produced does not work properly

Goitre

• Goitre is an enlarged thyroid gland. A goitre can mean that all the thyroid gland is swollen or enlarged, or one or more swellings or lumps develop in a part or parts of the thyroid.

• In some people, the goitre is associated with an abnormality of thyroid function. You may make too much thyroxine or T3 (hyperthyroidism or overactive thyroid) or too little thyroxine or T3 (hypothyroidism or underactive thyroid).