This will cause an action potential to spread down to the T- tubules and “electrical chemical signals = shocks” the sarcoplasmic reticulum into releasing calcium ions. Then the calcium is released from the sarcoplasmic reticulum to the sarcoplasm. 5. Calcium is restored/ reused in the sarcoplasmic reticulum. Just as concentration results from the release of calcium ions stored in the sarcoplasmic reticulum, contraction ends and relaxation begins as Calcium is
Outline the body’s response to stress (6 marks) There are two types of stress: acute and chronic stress. Acute stress (short-term stress) causes the body to respond through a process called the sympthomedullary pathways. This immediate response is achieved because of the hypothalamus’s direct link to the nervous system which causes the activation of the sympathetic nervous system (SNS). This is a branch from the autonomic nervous system. The SNS also regulates the sympathetic adrenal medullary system (SAM).
Homeostasis is the process of maintaining a constant internal environment in response to changes in the external environment. Homeostatic mechanisms are for regulating; body temperature, blood glucose, heart rate and breathing rate. Regulating the internal environment of a human is achieved by negative feedback; this is a constant process. Conditions within the body changes and receptors detect that change; receptors are found in the skin, around vital organs and the hypothalamus. This information of change that is detected by the receptors are then passed to the control centre in the hypothalamus which monitors the changes, when the change in environment fall too far outside the normal range of values the negative feedback response begins.
Graded potentials are electrical signals that have variable amplitude, are localized, and travel short distances along the membrane. In contrast, an action potential has a fixed amplitude, and can travel greater distances along the membrane. 3. a. Describe how there can be an electrical change on either side of a membrane thereby generating a membrane potential. The membrane potential is due to the presence of an ionic concentration difference and electrical gradient between both sides of the membrane.movement of charged molecules across the cellular membrane leads to the creation of electrical signals.
Atropine acts as an antagonist within the central nervous system, which means it acts as a blocker of specific cellular functions. What part of the autonomic nervous system does atropine block to produce its effect on Dr. Westwood? Atropine was administered in response to the bradycardia; after it was administered it brought up his blood pressure as well has his heart rate. Within the parasympathetic nervous system, Atropine blocks the muscarinic receptor which then blocks acetylcholine (Ach). Because of the blockage of Ach the muscarinic receptor antagonist can block the vagal nerve from affecting the heart, and can then increase the heart
Blood hormone concentrationare usually governed by negative feedback control – a reduction in concentration stimulates additional secretion and an increase in concentration inhibits further secretion. Once hormone binds to a receptor moleculethey are usually degraded rapidly. This ‘rapid recovery system’ mens that the target calls can be sensitive to changing levels of the hormones that regulate their
QAHS BIOLOGY CORE TOPIC E4 Neurotransmitters and Synapses E4.1 State that some presynaptic neurons excite postsynaptic transmission and others inhibit postsynaptic transmission. Some presynaptic neurons excite postsynaptic transmission and others inhibit postsynaptic transmission. Synapses are junctions between neurons Each neurone has many synapses with other neurons These synapses can be inhibitory or excitatory An action potential in the post synaptic neuron will only occur if the potential difference at the axon hillock rises above the threshold value. An impulse arrives through an excitatory neuron but the rise in potential difference is insufficient to reach the threshold and so
Homeostasis mechanisms control the body temperature, breathing rate, heart rate, blood glucose levels and many more. The body gives two types of feedback within the body – Negative feedback and Positive feedback. The internal environment is everything that consists within the body everything within the body must be kept within a certain range to allow the cells within the body to still function. Negative feedback is used when the body detects changed in the body and corrects them. These are the steps, Receptors in the nervous system detect a change in the body, Impulses are sent to the control centre, often the brain, and then impulses are sent from the effectors to counteract the change.
c) How does one nerve cell communicate with another? - Nerve cells communicate with one another through neurotransmitters. 2. a) Explain what neurotransmitters are? - Neurotransmitters are chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing where that neuron will generate a neural impulse.
Negative feedback is where various receptors and effectors cause a reaction to ensure certain conditions remain the same. It is an automatic, corrective mechanism within the body. An example of negative feedback is temperature control. If the blood temperature rises, a ‘heat gain’ centre in the brain sends nerve impulses to the skin, which causes vasodilation and sweating, which will cool down the blood. If the blood temperature falls, it stimulates a ‘heat loss’ centre in the brain which sends impulse to the skin, causing vasoconstriction and the cessation of sweating.