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Biology - Topic 5 - Homeostasis and Response (Hormones/Endocrine system…
Biology - Topic 5 - Homeostasis and Response
control systems
Receptors
: Receptors are groups of specialised cells that can detect changes in the environment called stimuli. Receptors are often located in the sense organs, such as the ear, eye and skin.
Examples
include
the eyes and light,
the ears with position of the head and sound
and also the tongue with chemicals in food.
Coordination Centre
: Once the receptors detect the stimuli being to high or too low the coordination centre processes the information and organises a response
Effector
: This produces the response which counteracts the change detected by the receptor, depending on what was detected the levels will increase or decrease to bring levels back to optimum. However the effectors can have a opposite effect as they will continue producing the responses so long as they’re stimulated by the coordination centre , shifting the balance the other way. The receptors would then detect this imbalance and the process would start again.
Examples
of this include:
Muscles contacting to move the arm
Muscle squeezing salaiva fro m the alivary gland
A gland releasing a hormone into blood
The automatic control system keep the environment stable and this mechanism is called
NEGATIVE FEEDBACK
The process bypasses the brains acknowledgement as it won’t notice the change until its complete. As it is automatic it happens without thinking about it..
The Nervous Sytem
The human nervous system consists of:
Central nervous system
-the brain and spinal cord
Peripheral nervous system
- nerve cells that carry information to or from the CNS
In vertebrates this consists of the brain and spinal cord only. In mammals the CNS is connected to the body by sensory neurons and motor neurons:
Sensory neurons
; The neurons that carry information as electrical impulses from the receptors that detect the change in the environment. Carry signals from receptors to the spinal cord and brain.
Relay Neuron
: Carry messages from one part of the CNS to another.
Motor Neurons
: The neurons that carry the impulses from the CNS to the effectors. Carry signals from the CNS to effectors.
Effector
: All muscle and glands that respond to the nervous impulses.
Organisms need to respond to stimuli in order to carry on the functions they continuously carry out. Single cell organisms do this independently whereas multi-cellular ones must communicate, hence the development of the nervous system.
HOW IT WORKS
Stimulus
: Bird sees cat
Receptor:
Stimulated
Sensory Neuron
: carry the information to the CNS
Relay Neuron
: Relay neurones carry messages from one part of the CNS to another
Motor Neuron
: CNS sends information on what to do via the motor neuron
Effector
: It may be to the muscles in the bird’s wings
Response
: Bird flies away
Reflex actions and synapses
reflex action
These are automatic and rapid - they do not involve the conscious part of the brain
this allows the body to rapidly respond to stimuli to prevent further damage:
stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response
Examples
A bright light- your pupils become smaller to allow less light and prevent damage.
Or a shock- your body sends the adrenaline hormone without waiting for a decision
The nerve pathway from
receptor to effector
is called a
reflex arc
function
enables human to react to surroundings
structure
brain and spinal cord - CNS central nervous system
receptors - gather information
neurones - transmit electrical impulses to CNS
Stimulus —> receptor —> coordinator —> effector —> response
considered response
this is a response where the information is communicated and the conscious part of the brain thinks and makes a decision that is carried out by the effector e.g. seeing a cake and reaching out to eat it
synapse
this is the junction between two neurones
the electrical impulse travels along the neurone until it reaches the synapse
there a small sacks of
neurotransmitters
( chemicals) at the end of the neurone
the electrical impulse causes these to be released into the synapse
the neurotransmitters
diffuse
across the gap and attach to receptors on the next neurone
this triggers an electrical impulse in the next neurone and the impulse continues the travel
THE BRAIN
Alongside the spine its part of the CNS.
It is made up of millions of interconnected neurons .
In charge of all complex behaviour ,
everything we do is controlled by the brain.
Different sections:
CEREBRAL CORTEX
The outer 'wrinkly' section, responsible for consciousness, intelligence, memory and language
MEDULLA
Controls unconscious stuff, such as breathing
CEREBELLUM
Controls muscle coordination.
How the Brain Is Studied
Brain damage:
If a small section of the brain has been damaged , this is useful as from the effects it has on the patient can determine a lot about that sections use. E.g Back section affects vision-patient went blind.
Electrical stimulation
Pushing a tiny electrode into part of the brain tissue gives it a small zap. The effects can be observed giving you a basis of what they do. E.g the motor area causes muscle contraction and movement. .
MRI Scans
A tube like machine that can produce detailed pictures of the brain and its structure. Can be used to find active areas during certain tasks.
How Messing With It Has Consequences
Knowledge of the workings of the brain had led to developments for treatment for disorders. For example electrical stimulation can reduce muscle tremors. However, any kind of observations is difficult due to complexity. Physical damage is a huge risk and can carny functional issues.
The EYE
The
sclera
is the tough wall of the eye there for support.
The
cornea
is what refracts light into the eye and is the transparent outer layer.
The
iris
allows you to control the diameter of the pupil and therefore the amount of light.
The
lens
focuses light onto the
retina
( the retina contains the cells that detect light sensitivity and visible colour)
The shape of the lens is determined by the
Cilia Muscle
and
Suspensory Ligaments
The
optic nerve
carries the impulses to the brain
The Iris
The eye is sensitive to light, therefore bright lights can leave it damaged so we have reflex that will protect us from it.
When
light receptors
detect bright light, the
circular muscle contracts
and the
radial muscle muscle relaxes
making the pupil smaller than it previously was, allowing less light.
The opposite in dim light
https://www.google.co.uk/search?q=diagram+of+eye&safe=strict&tbm=isch&source=iu&ictx=1&fir=v-K9-b5SVyXqbM%253A%252CxC7W3YlpfdXnTM%252C_&usg=__SDmzOtl0JDTF1S1C2OVb1S4e-f0%3D&sa=X&ved=0ahUKEwidkqSUyOzZAhWjJcAKHWOhBEEQ9QEILTAB#imgrc=v-K9-b5SVyXqbM
:
NIFTY EYE DIAGRAM THAT IS TOO SMALL HERE
Focusing on Near light and Distant objects
Near) The ciliary muscle contracts, slackening the suspensory ligament.
far) The opposite happens meaning the lens go thin (less curvature) and refracts a smaller amount of light
Correcting Vision
Long Sighted
the inability to focus on
near objects
1) Often the lens is the wrong shape poorly refracting light or the eyeball is too short.
2)The image is brought to focus behind the retina
3)Glasses with a convex lens are used (curves outwards) refracting light waves onto the retina
4)The medical term is
hyperopia
Short-sighted
cant focus on
distant
objects
1) Lens is wrong shape and refracts too much light,or eyeball is too long
2) The images are brought into focus in front of the retina
3)Glasses with a concave lens (Curves inwards), light focuses on retina
4) Medical term is
Myopia
Controlling Body Temperature
Body temperature needs to be controlled to allow optimum functioning of systems
or - by 4 can cause major problems ( enzymes denature or slow down too much and cellular reactions limited)
Body temperature regulated by thermoregulTory centre in the brain
Receptors in the thermoregulatory centre and some surface receptors in the skin gather information regarding body temperature
Too high
vaso dilation-blood vessels dilate,more blood flows closer to surface of skin,enenergy transferred from skin to surroundings
sweating-as sweat evaporates energy transferred From skin
hairs lie flat-no Air trapped
Too low
vaso constriction-less blood flowing closer to surface-less energy lost
no sweating
shivering
hairs stand on end
Hormones/Endocrine system
Endocrine system is composed of
glands
that secrete chemicals called hormones.
hormones
carried in the blood stream to the target organ where it produces a response
Nervous system vs endocrine system
NS electrical signals. ES. Chemical signals
NS rapid effect - short lived. ES slower effect that are longer lived
pituitary gland
known as the master gland
secretes several hormones
these hormones act on other glands to stimulate release of other hormones.
blood glucose regulation
glucose moves from blood into cells - liver stores glucose as glycogen
blood glucose
too high
-
insulin
released from pancreas
Blood glucose
too low
- pancreas releases
glucagon
monitored and controlled by the pancreas
glycogen converted into glucose and released into blood stream
water and ion regulation
Urea
- produced when excess amino acids are broken down by the liver. Form Ammonia which is converted to urea for safe excretion
Water ions and urea - lost from body in sweat (no control)
Kidneys
produce urine by ULTRAFILTRATION of the blood and selective reabsorption of useful substances
Water leaves the body via lungs in exhalation (no control)
Excess water ions and urea removed via the kidney - controlled
Kidney function
2 - All the glucose is reabsorbed into the blood (active transport)
3 - reabsorb dissolved ions - selective - active transport
1 - blood filtered as it enters the kidney - large molecules (proteins) and blood cells remain in the blood
4 - reabsorb water - controlled by Pituitary releasing Anti Diuretic Hormone (
ADH
) too much water - less ADH released - less water reabsorbed - more uring produced. Too little water - more ADH released - more water reabsorbed - less urine produced
ADH affects the permeability of the kidney tubule - makes it easier for water to be absorbed
Kidney failure
Organ transplant - disadvantages - waiting list - risk of rejection - immunosuppressant drugs (anti rejection drugs)
Dialysis - advantages - replaces role of failed kidney - keeps patient alive while waiting for donor
Dialysis disadvantages - long hours spent on dialysis - diet carefully controlled
Organ transplant - advantages - prolong life, not tied to restrictive diet, do not have to attend dialysis
Dialysis - Arterial blood from patient passes through dialysis - blood flows through partially permeable tubing - dialysis fluid surrounds tubing - flows in opposite direction to blood flow (maintains concentration gradient) Dialysis fluid - contains No Urea (so urea moves OUT of the blood) Contains correct concentration of glucose water and ions - this allows movement of these substances into or out of blood to establish the desired levels.
Menstrual cycle
Females -
oestrogen
main female hormone, menstrual cycle begins during puberty which is controlled by hormones
follicle stimulating hormone (FSH)
produced by pituitary, causes maturation of eggs
Puberty - reproductive hormones cause secondary sexual characteristics to develop
Luteinising hormone -
stimulates the release of the egg from the ovary - ovulation
Oestrogen
- causes the thickening of the lining of the uterus
Males -
testosterone
- main male sex hormones - produced in testes - stimulates sperm production
