Transcript Coordination of the human body

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 systems
Nervous
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
Brain
Spinal Cord
Peripheral nervous system
Visceral nervous
Somatic Nervous
system (autonomic)
system (voluntary)
Sympathetic
nervous system
Spinal Nerves
only
Spinal Nerves
Parasympathetic
nervous system
Cranial Nerves
Spinal Nerves
Cranial Nerves
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 / Parasympathetic
The 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".
Neurones
Nerves 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
Touch
Smell
Hearing
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.
Synapses
The 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.
EEG
An 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 to
Diagnose epilepsy
Check for problems with loss of consciousness
Find out if a person who is in a coma is braindead.
Study sleep disorders
Watch 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
Pituitary
gland
Thyroid
Hormone
Prolactin, FSH, LH, thyroid stimulating (TSH),
adrenocortictrophic (ACTH) growth
hormone
Triidothyronine, thyroxine, calcitonin
Adrenal
medulla
Kidney
Adrenaline
Ovarian
follicle
Oestrogen, progesterone
Renin
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
increase
decrease
Insulin production
stops glucagon
secreted.
Glycogen to
glucose
Insulin released
from pancreas
Level returns to
normal
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).