Autonomic and endocrine systems L5

Question 1

Components of the PNS

Answer 1

Cranial nerves, spinal nerves, ganglia

Question 2

Components of the CNS

Answer 2

Brain, spinal cord

Question 3

What is the name for the nerves that are going into the central nervous system? (CNS)

Answer 3

Sensory (afferent) neurons

Question 4

What is the name for the nerves that are going out from the central nervous system? (CNS)

Answer 4

Motor (efferent) neurons

Question 5

Types of motor (efferent) neurons

Answer 5

Somatic (voluntary) -> Skeletal muscle

Autonomic (involuntary) ->
Sympathetic
+ Parasympathetic -> Cardiac muscle, smooth muscle, and glands

Question 6

Structure of neurons

Answer 6

Question 7

Myelinated nerve

Answer 7

Question 8

Unmyelinated nerve

Answer 8

Question 9

How does nerve synapse work?

Answer 9

Question 10

Process of synaptic transmission

Answer 10

Nerve Impulse Arrival:
A nerve impulse (or action potential) travels down the axon of a neuron and reaches the synaptic terminal.

Opening of Voltage-Gated Calcium Channels:
The action potential triggers the opening of voltage-gated calcium (Ca²⁺) channels located in the membrane of the presynaptic neuron.
As a result, calcium ions (Ca²⁺) flow into the presynaptic terminal due to the concentration gradient (more Ca²⁺ outside the neuron).

Neurotransmitter Release:
The influx of Ca²⁺ causes synaptic vesicles (small membrane-bound sacs containing neurotransmitters) to fuse with the presynaptic membrane.
This process, called exocytosis, releases neurotransmitters (such as acetylcholine or glutamate) into the synaptic cleft, the small gap between the presynaptic and postsynaptic neurons.

Binding to Receptors:
The neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic membrane.
These receptors are often ligand-gated ion channels, which open upon neurotransmitter binding, allowing ions to flow into the postsynaptic neuron.

Post-Synaptic Response:
Depending on the type of neurotransmitter and receptor, the postsynaptic neuron may become excited (depolarized, leading to an action potential) or inhibited (hyperpolarized, making it less likely to fire an action potential).
The neurotransmitter action is terminated either by enzymatic breakdown, reuptake into the presynaptic neuron, or diffusion away from the synaptic cleft.

Question 11

What do nerves do?

Answer 11

Co-ordinate our actions and bodily functions

Question 12

Divisions of the autonomic nervous system

Answer 12

Sympathetic and Parasympathetic

Question 13

What happens when we sense a potential threat?

Answer 13

Our brain triggers a chain of reactions to ensure our survival. First it activates the sympathetic nervous system, where the brain sends an electrical message to the adrenal glands, which flood the body with adrenaline. This initiates the short-term energy burst needed to respond to the emergency.

Answer 14

As the message travels through our body, our pupils dilate to increase the information coming in, our muscles tense up and our breathing becomes fast and shallow to bring more oxygen to our blood. - Heart rate increases and contraction force as well
- Also decrease in saliva in your mouth.
- Bronchi also dilate in your lungs and you breathe faster.
- Skin:
- constrict peripheral arterioles
- constrict arrector pili muscles (hair on your skin)
- increase sweat secretion
- Gut:
- Decrease digestion
- Increase blood sugar

Question 15

The relaxation/parasympathetic response

Answer 15

Heart: Decrease rate and contraction force
Eyes: Contract pupils
Mouth: Increase saliva
Lungs: Constrict bronchi, breathe more slowly (lower gas exchange)
Skin: Dilate peripheral arterioles
Gut: Increase digestion

Question 16

What is the sympathetic division associated with?

Answer 16

• Exercise
• Emotion
• Excitement
  (Alarm response)

Question 17

What is the parasympathetic division associated with?

Answer 17

• Relaxation
• Rest
• Repletion
  (Relaxation response)

Question 18

Sensory input in Somatic system

Answer 18

Special senses and somatic senses

Question 19

Sensory input in Autonomic system

Answer 19

Mainly interoceptors

Question 20

Control of output in Somatic system

Answer 20

Voluntary from cerebral cortex

Question 21

Control of output in Autonomic system

Answer 21

Involuntary from limbic system, brain stem, and spinal cord

Question 22

Effectors of the somatic system

Answer 22

Skeletal muscle

Question 23

Effectors of the autonomic system

Answer 23

Smooth muscle, cardiac muscle, glands

Question 24

Process of the Somatic Nervous System

Answer 24

Function: The SNS is responsible for voluntary control of skeletal muscles.
Pathway:
Motor Neuron: The pathway involves a single motor neuron that extends directly from the spinal cord to the skeletal muscle.
The motor neuron is myelinated, meaning it has a myelin sheath that increases the speed of nerve impulse conduction.
The neurotransmitter released at the synapse between the motor neuron and the muscle is acetylcholine, which stimulates muscle contraction.
Effector: The effector in the SNS is skeletal muscle, which responds to acetylcholine by contracting.

Question 25

Process of Autonomic Nervous System

Answer 25

Function: The ANS controls involuntary bodily functions, such as heart rate, digestion, and respiratory rate. It regulates the function of internal organs and glands.
Pathway:
The ANS involves a two-neuron chain:
A preganglionic neuron (myelinated) extends from the spinal cord to an autonomic ganglion (a cluster of nerve cells).
A postganglionic neuron (unmyelinated) extends from the autonomic ganglion to the target organ (e.g., smooth muscle, cardiac muscle, or glands).
The preganglionic neuron releases acetylcholine at the ganglion, while the postganglionic neuron releases either acetylcholine or norepinephrine depending on whether it is part of the parasympathetic or sympathetic division of the ANS.
Effector: The effectors in the ANS are smooth muscle, cardiac muscle, and glands. The response can either be stimulatory or inhibitory, depending on the neurotransmitter released.

Question 26

What does the Somatic Nervous System control?

Answer 26

Voluntary movements

Question 27

What does the Autonomic Nervous System (ANS) control?

Answer 27

Involuntary functions. The ANS has two key divisions: the sympathetic and parasympathetic systems.

Question 28

Sympathetic =

Answer 28

“Fight or flight” (stress response)

Question 29

Parasympathetic =

Answer 29

“Rest and digest” (relaxation and recovery)

Question 30

Sympathetic division (autonomic)

Answer 30

Preganglionic Neuron:
This neuron originates from the spinal cord and releases acetylcholine (ACh) at the synapse in the ganglion (the first junction).
Ganglion:
The ganglion is a relay point where the preganglionic neuron communicates with the postganglionic neuron.
Postganglionic Neuron:
This neuron extends from the ganglion to the target organ or effector cell.
It releases norepinephrine (noradrenaline) at the second synapse, which then acts on the effector cell (in this case, a muscle cell or organ).
Effector Cell:
The effector cell is the target tissue or organ, which receives the signal. In the top part of the diagram, norepinephrine binds to receptors on the effector cell to induce a response (like increased heart rate, pupil dilation, etc.).

Special Case - Sweat Gland Cells:
In the lower part of the diagram, the postganglionic neuron releases acetylcholine (ACh), which acts on sweat glands. This is an exception, as most sympathetic postganglionic neurons release norepinephrine.

Question 31

Parasympathetic division (autonomic)

Answer 31

Preganglionic Neuron:
Similar to the sympathetic system, the preganglionic neuron originates in the CNS (brainstem or spinal cord) and extends to a ganglion.
It releases acetylcholine (ACh) as the neurotransmitter at the ganglionic synapse.
Ganglion:

The ganglion is where the preganglionic neuron synapses with the postganglionic neuron.
The ganglia in the parasympathetic division tend to be located closer to the target organs (unlike the sympathetic system, where ganglia are closer to the spinal cord).

Postganglionic Neuron:
This neuron extends from the ganglion to the effector organ (like the heart, lungs, or digestive organs).
The postganglionic neuron also releases acetylcholine (ACh) at the synapse with the effector cell, unlike the sympathetic system where norepinephrine is typically released.

Effector Cell:
The effector cell is the target organ or tissue (like smooth muscle, glands, or cardiac muscle) that responds to the neurotransmitter acetylcholine to carry out parasympathetic functions such as slowing heart rate, promoting digestion, or constricting pupils.

Question 32

Somatic vs Autonomic table

Answer 32

Question 33

What is raynaud disease?

Answer 33

Happens when their sympathetic system gets activated in situations of stress or situations of exposure to cold and various other things, but does not turn down as quickly as they should - therefore cold hands.

Question 34

Process of raynaud disease

Answer 34

Excessive Sympathetic Stimulation:
Raynaud disease is triggered by overactivation of the sympathetic nervous system, often in response to emotional stress or exposure to cold.
When the sympathetic nervous system is activated, norepinephrine (a neurotransmitter) is released. This neurotransmitter acts on receptors in the smooth muscle lining of blood vessels.
In particular, it stimulates alpha-adrenergic receptors on the smooth muscle surrounding arterioles (small arteries), which supply blood to tissues.
When these receptors are activated, the smooth muscles contract, causing vasoconstriction, which reduces the diameter of the blood vessels.
This overactivation leads to vasoconstriction (narrowing of blood vessels), which limits blood flow to certain areas, typically the fingers and toes.

Chronic Vasoconstriction:
The condition involves chronic vasoconstriction, meaning the blood vessels remain narrowed for an extended period. This reduces the amount of blood reaching the affected areas, causing them to become ischemic (lack of blood supply).

Ischemia and Appearance:
As the image highlights, ischemia (lack of blood flow) causes the fingers and toes to become pale or even white. This happens because the lack of oxygenated blood causes the tissues to lose color.
In severe cases, it can progress to blue discoloration (cyanosis) or red as blood flow returns.

Question 35

How does the hypothalamus control internal organs?

Answer 35

Controls internal organs via:
- Autonomic nervous system
- Pituitary gland

Question 36

What does the hypothalamus regulate?

Answer 36

• Behaviour patterns
• Circadian rhythm (sleep/wake cycles)
• Body temperature
• Eating and drinking

Question 37

What organs are the central trunk of the endocrine system?

Answer 37

The hypothalamus, pituitary, adrenal glands

Question 38

Name the endocrine system

Answer 38

Question 39

Endocrine hormones and how they work

Answer 39

Endocrine Cell:
The endocrine cell is a specialized cell that produces and releases hormones. Endocrine cells are found in various glands throughout the body, such as the thyroid, adrenal glands, pancreas, and pituitary gland.

Circulating Hormones:
Once released by the endocrine cell, the hormone enters the bloodstream (blood capillary) and circulates through the body.
These hormones travel via the blood to distant organs and tissues to exert their effects. This is different from local hormone signaling (like paracrine or autocrine signaling) where hormones act on nearby cells.

Distant Target Cells:
The hormone travels in the bloodstream until it reaches target cells that are often far away from the gland that secreted the hormone.
These target cells have specific receptors that are shaped to bind to the hormone. Only cells with the correct receptor can respond to the hormone, making the signaling process specific.

Hormone Receptor:
The target cells have specialized hormone receptors on their surface. When the hormone binds to these receptors, it triggers a specific response within the cell. This response could range from changes in gene expression to alterations in cellular metabolism or growth.

Question 40

Paracrine hormones

Answer 40

Paracrine signaling is a form of localized communication between cells. Unlike endocrine hormones that travel through the bloodstream to act on distant cells, paracrine hormones act locally and affect cells that are in close proximity to the cell that secreted them.

Question 41

Autocrine hormones

Answer 41

In autocrine signaling, the cell releases signaling molecules (hormones) that bind to receptors on itself. This allows the cell to regulate its own behavior.

Question 42

Control of hormone release

Answer 42

Question 43

Lipid-soluble hormones

Answer 43

Step 1: Hormone Transport and Diffusion into the Cell
Lipid-Soluble Hormones:
These hormones travel in the bloodstream, often bound to transport proteins to help them move through the water-based blood plasma.
Once at the target cell, the free hormone (not bound to transport proteins) diffuses through the cell membrane because it is lipid-soluble and can easily pass through the phospholipid bilayer.
Step 2: Formation of Hormone-Receptor Complex
Once inside the cell, the hormone binds to intracellular receptors, usually located in the cytoplasm or directly in the nucleus.
The hormone-receptor complex then enters the nucleus (or binds to nuclear receptors if already present) and interacts with specific genes on the cell’s DNA.
This binding alters gene expression by either increasing or decreasing the transcription of specific genes.
Step 3: mRNA and Protein Synthesis
When the hormone-receptor complex binds to the DNA, it stimulates the production of messenger RNA (mRNA). This mRNA carries the genetic instructions for synthesizing specific proteins.
The mRNA then moves out of the nucleus and into the cytoplasm, where it directs the ribosomes to create new proteins based on the instructions from the mRNA.
Step 4: New Protein Alters Cellular Activity
The newly synthesized proteins then perform specific functions within the cell, altering the cell’s behavior or function.
For example, these proteins might regulate metabolic processes, influence growth, or modify the structure and function of the cell.

Question 44

Water-soluble hormones

Answer 44

Step 1: Binding to Receptor and Activation of G Protein
Water-soluble hormones (like epinephrine, insulin, and glucagon) bind to a receptor located on the cell membrane because they cannot pass through the lipid bilayer.
The hormone binding activates a G protein, which is linked to the receptor. This G protein activates an enzyme called adenyl cyclase inside the cell.
Step 2: Conversion of ATP to cAMP
Adenyl cyclase (the enzyme activated by the G protein) converts ATP (adenosine triphosphate) into cAMP (cyclic adenosine monophosphate).
cAMP acts as a second messenger inside the cell, amplifying the signal from the hormone-receptor binding.
Step 3: cAMP Activates Protein Kinases
The cAMP then activates protein kinases. Protein kinases are enzymes that add phosphate groups to other proteins (a process called phosphorylation).
Step 4: Phosphorylation of Other Enzymes
The activated protein kinases phosphorylate various target proteins and enzymes within the cell. This phosphorylation changes the activity of these enzymes, allowing them to catalyze specific reactions or perform other cellular functions.
Step 5: Cellular Response
The phosphorylation of enzymes triggers physiological responses. These responses could involve metabolism, ion transport, secretion of other hormones, or other cellular functions depending on the hormone’s role.
Step 6: Inactivation of cAMP
Phosphodiesterase is an enzyme that breaks down cAMP, ensuring that the signal from the hormone is temporary and tightly regulated. Once cAMP is degraded, the effects of the hormone are terminated.

Question 45

Cholera Mechanism of Action:

Answer 45

Cholera Toxin Locks G Protein in the Activated State:

Cholera toxin binds to the G protein on intestinal cells (specifically on the cell membrane).
Normally, G proteins are activated temporarily in response to a signal (such as a hormone binding to a receptor) and then deactivate. However, cholera toxin locks the G protein in its active state.
High Levels of cAMP:

Once the G protein is locked in the active state, it continuously activates the enzyme adenyl cyclase.
This leads to an overproduction of cyclic AMP (cAMP), a secondary messenger that amplifies the cellular signal and is involved in many cellular processes.
Chloride Ions Pumped into the Intestines:

High levels of cAMP cause ion channels in the intestinal epithelial cells (like the CFTR channel) to remain open, leading to the continuous pumping of chloride ions into the intestinal lumen (the inside of the intestines).
Water Follows the Ions:

Chloride ions being pumped into the intestines creates a concentration gradient, drawing sodium and water into the intestines via osmosis.
This results in a large amount of water entering the intestinal lumen, leading to the characteristic watery diarrhea of cholera.