regulatory body systems

Question 1

what is the endocrine system?

Answer 1

1. made up of a collection of glands
2. the glands synthesise and secrete signalling molecules called hormones into the bloodstream

Question 2

what are hormones?

Answer 2

1. are produced by the endocrine system
2. chemical messengers
3. have target cells and organs
4. not all cells respond to all hormones
5. two types of hormones, steroid hormones and non-steroid hormones.
6. they travel through the bloodstream to their target tissues. target tissues have receptors for specific hormones. hormone receptors are substrate-specific. only cells with complementary receptors will be able to bind that hormone and respond.
7. cause long responses, and can have more than one type of target cell.

Question 3

what are examples of these hormones?

Answer 3

1. adrenaline
   gland: adrenal medulla
   target tissues: heart, blood vessels, liver, etc
   main functions: increases heart rate, blood pressure, releases stored glucose from the liver, prepares the body for action.
2. insulin
   gland: pancreas
   target tissues: liver, fat tissue, muscle tissue
   main function: decreases blood glucose
3. glucagon
   gland: pancreas
   target tissues: liver, fat tissue
   main function: increases blood glucose
4. thyroxine
   gland: thyroid
   target tissues: most cells in the body
   main function: regulates cellular metabolism

Question 4

what are steroid hormones?

Answer 4

1. made from cholesterol
2. are lipid soluble
3. have receptors inside the target cells
4. are responsible for switching the transcription of genes on or off.
   e.g, sex hormones like oestrogen, testosterone, progesterone.
5. steroid hormone response mechanism: they pass through the plasma membrane since they are lipid soluble. steroid hormones bind to their receptors in the cytosol or in the nucleus of the cell. once bound to the receptor, the activated hormone-receptor complex moves into the nucleus. the complex binds to specific parts of the DNA. this activates the gene, increasing the production of the protein that the gene codes for.

Question 5

what are nonsteroid hormones?

Answer 5

1. made of proteins or peptides
2. water soluble to varying degrees
3. generate second messengers inside the target cell
4. are responsible for changing enzyme activity inside the target cell
   e.g, glucagon, insulin
5. nonsteroid hormone response mechanism:
   nonsteroid hormones are water-soluble, thus they cannot pass through the plasma membrane by simple diffusion. receptors for nonsteroid hormones are on the surface of cells. when the hormones bind to the receptors, second messengers are made and activated in the cytoplasm of the cell. second messengers trigger the synthesis or activation of specific enzymes. the enzymes cause the synthesis of a specific cell product. one hormone-receptor complex can start the production of many second messengers. this increases the speed and strength of the response.

Question 6

what is the nervous system?

Answer 6

1. involves neurons which are specialised cells that transmit messages around the body. they connect to form the NS

Question 7

what are the structures of a neuron and their functions?

Answer 7

1. dendrites: branching structures that connect to and receive information from other cells and carry it towards the soma
2. soma: contains the nucleus and carries out all functions needed to keep the cell alive
3. axon: long section that transmits the electrical signal away from the soma towards other cells
4. myelin sheath: a fatty substance that wraps around the axon to insulate and speed up the signal
5. schwann cells: cells that produce the myelin sheath
6. synaptic terminals: branches of the axon that allow multiple connections to other cells
7. terminal buttons: the end of the axon terminals that release neurotransmitters into the synaptic gap.

Question 8

what are the 3 types of neurons?

Answer 8

1. sensory neurons:
   - afferent neurons
   - connect to receptors (specialised cells that detect stimuli)
   - transmits stimulus information
2. motor neurons:
   - efferent neurons
   - transmit response information
   - connect to effectors (specialised tissues/organs that carry out the response)
3. interneurons:
   - called connector neurons
   - link sensory neurons with motor neurons
   - receive, analyse and interpret sensory information

Question 9

what is a neural transmission?

Answer 9

1. a combination of electrical signals and chemical secretions through the nervous system
2. the electrical impulse is caused by an action potential. travels from the dendrites to the synaptic terminals like a wave.
3. a neuron that is not responding to a stimulus is ‘at rest’. a small difference in electrical charge exists across the resting cell membrane. the outside of the cell membrane of the axon is positively charged compared to the inside. this difference in charge is called the resting potential of the membrane
4. the impulse starts in a section of membrane where the resting potential changes. the threshold of stimulation is required to trigger the action potential. when the threshold is reached, the permeability of the membrane is changed

Question 10

what is the speed of transmission?

Answer 10

1. nerve impulses travel faster along myelinated axons
2. nodes of Ranvier also speed up transmission because the impulse can ‘jump’ the gaps
3. myelin also insulates axons from each other, prevents the signals of different neurons from getting mixed up.

Question 11

what are chemical signals between neurons?

Answer 11

1. synapse; point where a neuron connects w/ another cell
2. synaptic cleft; separates the two cells
3. action potential cannot cross this gap. synaptic terminals secrete chemicals called neurotransmitters which diffuse across the gap
4. when the action potential arrives at the end of the axon terminals of the presynaptic neuron, calcium ions diffuse down the synaptic terminals. these ions cause vesicles containing neurotransmitters to fuse with the membrane, releasing neurotransmitters into the synaptic cleft. these neurotransmitters diffuse across the gap and bind to specific receptors on the dendrites of the postsynaptic neuron.

Question 12

what is the central nervous system?

Answer 12

• made up of all neurons of the brain and spinal cord
• control centre

Question 13

what is the peripheral nervous system?

Answer 13

1. made up of the motor nervous system and sensory nervous system
2. motor nervous system: motor neurons carry signals from the CNS to the effectors
3. sensory nervous system: sensory neurons carry stimulus info to the CNS
4. motor nervous system is made up of the autonomous nervous system and somatic nervous system.
5. ANS: involuntary system, responsible for homeostasis, has two connections to effectors so it can control opp responses
6. SNS: voluntary system, connects to skeletal muscles and controls voluntary movement of the body
7. the ANS is made up of the sympathetic nervous system and parasympathetic nervous system
8. the sympathetic nervous system is responsible for preparing the body for action. often called the flight or fight response
9. parasympathetic nervous system is responsible for returning the body to a normal, calm state and maintaining normal functioning, ‘ rest and digest’.

Question 14

what are reflexes?

Answer 14

1. spinal cord is the coordinator.
2. are faster than normal responses
3. are automatic and don’t require you to think about them
4. help avoid damage to the body, esp to delicate or sensitive parts, like sensory organs.