Topic 2 – Responses to a Changing Environment

Topic 2 – Responses to a Changing Environment

Homeostasis Homeostasis means “controlling internal conditions”: Produced by respiration, removed via lungs Produced by liver breaking down amino acids, removed by kidneys and transferred to bladder Increased by shivering, lost by sweating Increased by eating, lost by sweating + urine Increased by drinking, lost by sweating + urine Increased and decreased by hormones

Homeostasis in different conditions

Body Temperature Nerve endings in the skin detect the external temperature Temperature detectors in the brain detect the blood temperature The hypothalamus coordinates a response using hormones Effectors (muscles and sweat glands) carry out the response

Maintaining Body Temperature Vasodilation Cold Hot Vasoconstriction

Heat stroke and hypothermia What does your body do to try to keep body temperature constant?

Controlling Water Content Low blood water level causes a high salt concentration Receptors in the hypothalamus detect the high salt content More ADH is secreted into the blood The kidney becomes more permeable to water so more is absorbed. The bladder fills with a small quantity of urine Normal blood water level is achieved.

Controlling Water Content 2 High blood water level causes a low salt concentration Receptors in the hypothalamus detect the low salt content Less ADH is secreted into the blood The kidney becomes less permeable to water so more is absorbed. The bladder fills with a large quantity of urine Normal blood water level is achieved.

Hormones The adrenal gland Hormones are “chemical messengers” produced by endocrine _____. They control the way in which parts of the body work and are transported to their target organs in the _______. Some examples... • The pancreas produces _______ • The adrenal gland produce ________ • The pituitary gland produces FSH and LH • Testes produce __________ • Ovaries produce progesterone Words – testosterone, glands, bloodstream, insulin, adrenaline

Controlling Blood Sugar levels If glucose levels fall too low then the hormone glucagon is released from the pancreas which causes liver to turn glycogen back into glucose If blood sugar is too high the pancreas releases insulin. Insulin lowers blood glucose levels by converting glucose into insoluble glycogen. We need glucose in our bodies to help our cells to respire and produce energy. What happens if we have too much glucose?

Diabetes What is diabetes? What do the pens (above right) do? What does an insulin injection (above left) do? What is the difference between Type 1 and Type 2 Diabetes? How does physical activity affect Type 1 and Type 2 Diabetics?

Diabetes Type 1 Diabetes is a ________ in which a person’s blood sugar (i.e. glucose) level may rise to a _______ level. This is because the ______ doesn’t produce enough _________.Physical activity will _______ the amount of glucose needed by the body. Diabetes can be treated by __________ carefully or by injecting extra insulin when needed. Diabetics have to test their blood sugar level before they decide how much insulin to _______ themselves with. Type 2 Diabetes occurs when the patient becomes _______ to insulin so the patient will have to be careful regarding physical activity. Words – insulin, disease, inject, dangerous, eating, pancreas, increase, resistant

Body-Mass Index Mass (kg) Height2 (m2) BMI = A commonly-used way to indicate is someone is overweight or underweight is the Body Mass Index (BMI):

Diabetes and Obesity % obesity of US population No. of people (in millions) with Diabetes

More interesting statistics… No. of fast food outlets No. of people (in millions) with Diabetes

Plant Hormones In the shoots the hormone auxin is “destroyed” by light, so the shoot will bend towards the light as the cells on the shaded side grow quickest. In the roots hormones slow down growth of the cells in the lower region, which makes the root bend down. The growth of roots and shoots is controlled by hormones:

Some Definitions Shoots grow towards light (positive phototropism) and against gravity (negative geotropism). Roots grow away from light (negative phototropism) and in the direction of gravity (positive geotropism).

Artificial Plant Hormones Hormones can be used to help plant growth and the development of fruit: 1) Auxin 2) Ethene This hormone helps fruit to develop This hormone helps fruit to ripen Other uses include rooting powders (to help root development), control of dormancy and weedkilling.

The Nervous System

The Nervous System The NERVOUS SYSTEM enables us to react to our surroundings. It consists mainly of the brain, the spinal chord, nerve cells (“neurones”) and receptors. • Types of receptor: • Light receptors in the eyes • Sound receptors in the ears • Taste receptors on the tongue • Smell receptors in the nose • Touch, pressure and temperature receptors in the skin • Changes of position receptors in the ears (balance)

Nervous Reactions Stimulus Receptor Coordinator Effector Response When we react to a stimulus our bodies use the following pattern: For example, consider a man and a camel: Oh No! What are the stimulus, receptor, coordinator, effector and response in this situation?

Examples of reactions

Structure of a nerve cell Nucleus Muscle strands (effector) Cell body Axon Myelin sheath – increases the speed of transmission Dendrons – conduct the impulse to the cell Impulse Impulse 1) Motor neurone 2) Sensory neurone 3) Relay neurone

Conscious actions 4) The brain decides to move away the hand 3) Here another sensory neurone carries the signal to the brain 5) This impulse is sent by MOTOR NEURONES to the hand muscles (the effectors) via the spinal chord… 2) The impulse is carried by SENSORY NEURONES to the spinal chord 1) Receptors in your skin detect a stimulus 6) Which then moves the hand away Stimulus Receptor Sensory Neurone Coordinator Motor Neurone Effector Response A conscious action is one where the brain makes a considered response. Here’s what happens:

Reflex actions Sometimes conscious action is too slow to prevent harm, e.g… In situations like this the body bypasses the brain to produce a quicker response. Here’s how it works…

Reflex actions 3. Relay neurone in the spinal chord 2. Sensory neurone 4. Motor neurone 1. Receptor 5. Effector

Synapses Neurones never ____ each other – there is a small gap between them called a _____. A signal is sent from one _______ to the next by a _______ transmitter across the synapse. These neurotransmitters are then ________. Words – chemical, synapse, neurone, touch, destroyed

Topic 2 – Responses to a Changing Environment