Integrative Autonomic (Make sure to do the tables first) LEC

What is the primary function of the Sympathetic Nervous System (SNS)?

The main function of the SNS is to prepare the body for 'fight or flight' responses.

What are the physiological changes associated with SNS activation?

Increased blood flow to skeletal muscles, elevated heart rate, increased blood pressure, heightened blood sugar level, and pupillary dilation (mydriasis).

What is the primary function of the Parasympathetic Nervous System (PNS)?

The main function of the PNS is to control 'rest and digest' activities.

What are the physiological changes associated with PNS activation?

Decreased heart rate, increased activity of the gastrointestinal tract, and pupillary constriction (miosis).

What neurotransmitter is primarily released by sympathetic nerves?

Norepinephrine is primarily released by sympathetic nerves.

What neurotransmitter is primarily released by parasympathetic nerves?

Acetylcholine is primarily released by parasympathetic nerves.

What is the structure and ratio of sympathetic nerve fibers involved in adrenergic transmission?

Sympathetic transmission involves a short cholinergic preganglionic fiber and a long adrenergic postganglionic fiber, with a ratio of preganglionic fibers to postganglionic fibers of 1:20.

What is the structure and ratio of parasympathetic nerve fibers involved in cholinergic transmission?

Parasympathetic transmission involves a long cholinergic preganglionic fiber and a short cholinergic postganglionic fiber, with a ratio of preganglionic fibers to postganglionic fibers of 1:3.

Describe the processes involved in cholinergic transmission.

1. Acetyl-CoA is synthesized in mitochondria.

2. Choline is transported into the neuron terminal by a sodium-dependent carrier (CHT1).

3. Choline and acetyl-CoA combine, catalyzed by choline acetyltransferase (ChAT).

4. Acetyl-CoA is transported into vesicles by the vesicular Acetyl-CoA transporter (VAChT).

5. Acetyl-CoA is released when an action potential triggers calcium influx.

6. Acetyl-CoA binds to nicotinic or muscarinic receptors on the postsynaptic membrane.

7. Autoreceptors (M2) inhibit further release.

8. Acetylcholinesterase (AChE) breaks down acetyl-CoA into choline and acetate.

Describe the processes involved in adrenergic transmission.

1. Tyrosine is transported into the adrenergic neuron via system L.

2. Tyrosine is converted to L-DOPA by tyrosine hydroxylase.

3. DOPA is converted to dopamine by DOPA carboxylase.

4. Vesicular monoamine transporter (VMAT) translocates dopamine into synaptic vesicles.

5. Intravesicular dopamine-beta-hydroxylase converts dopamine to norepinephrine.

6. Norepinephrine is released into the synaptic cleft.

7. Norepinephrine binds to alpha or beta adrenergic receptors on the postsynaptic membrane.

8. Autoreceptors (alpha2) inhibit norepinephrine release.

9. The action of norepinephrine is terminated by diffusion away from receptors and reuptake mediated by the Na+-dependent norepinephrine transporter (NET).

What is pupillary constriction and which autonomic function regulates it?

Pupillary constriction, known as miosis, is regulated by the parasympathetic nervous system. This process involves the circular muscle of the iris, which is innervated by M3 receptors, promoting aqueous humor outflow.

What is pupillary dilation and which autonomic function regulates it?

Pupillary dilation, known as mydriasis, is regulated by the sympathetic nervous system. This process involves the radial muscle of the iris, which is innervated by α1 receptors.

What is accommodation in relation to the eye and which autonomic function is involved?

Accommodation is the process that allows the eye to focus on near objects and is regulated by the parasympathetic nervous system through the ciliary muscle, which is activated via M3 receptors.

How is aqueous humor production regulated in the eye?

Aqueous humor production is regulated by the sympathetic nervous system through β1 and β2 receptors.

What autonomic functions are involved in the elevation of the upper eyelid?

Upper eyelid elevation is regulated by autonomic innervation of the superior tarsal muscle.

What are the functions of the baroreflex?

The baroreflex regulates blood pressure by adjusting heart rate, peripheral resistance, and cardiac output in response to changes in blood pressure.

What are the afferent pathways involved in the baroreflex?

Afferent information includes sensory input from the viscera, indicating a drop in blood pressure, which leads to reduced stretch of baroreceptors in the aortic arch and a reduced frequency of afferent impulses to the medulla (brainstem).

What are the efferent pathways involved in the baroreflex?

Efferent reflex impulses via the autonomic nervous system cause inhibition of the parasympathetic division and activation of the sympathetic division, leading to increased peripheral resistance and cardiac output, ultimately increasing blood pressure.

What stimuli trigger the baroreflex?

The primary stimulus for the baroreflex is a drop in blood pressure, which results in decreased stretch of the baroreceptors.

What are the clinical implications of baroreflex dysfunction?

Baroreflex dysfunction can lead to conditions such as orthostatic hypotension, blood pressure instability, and impaired cardiovascular responses to stress or changes in body position.

What is unique about the adrenal medulla in the sympathetic nervous system?

The adrenal medulla is directly innervated by preganglionic sympathetic fibers, and post-ganglionic neurons secrete epinephrine (E) and norepinephrine (NE) directly into the bloodstream.

How are sweat glands innervated in the sympathetic nervous system?

Sweat glands are innervated by cholinergic sympathetic postganglionic neurons, and the receptors on the sweat glands are cholinergic muscarinic: M3.

What is the role of the renal sympathetic nervous system?

In the kidneys, post-ganglionic sympathetic nerves secrete both norepinephrine (NE) and dopamine as neurotransmitters, with dopaminergic sympathetic postganglionic neurons supplying the renal vascular smooth muscles.

What type of receptors are found on renal vascular smooth muscles?

The receptors on the renal vascular smooth muscles are dopaminergic: D1.

What initiates cholinergic and adrenergic transmissions in the presynaptic terminal?

The arrival of an action potential at the presynaptic terminal initiates the process.

What happens after the action potential arrives at the presynaptic terminal?

Calcium channels open.

What occurs following the opening of calcium channels in cholinergic and adrenergic transmission?

There is an influx of calcium into the presynaptic terminal.

What is the role of calcium in neurotransmitter release?

Calcium binds with synaptic vesicles, leading to the release of neurotransmitters.

What happens after neurotransmitters are released into the synaptic cleft?

Neurotransmitters bind with postsynaptic receptors.

What is the final outcome of neurotransmitter binding in cholinergic and adrenergic transmissions?

There is a response in the postsynaptic cell.

What are organophosphate compounds and their relation to AChE?

Organophosphate compounds are acetylcholinesterase (AChE) enzyme inhibitors, which include insecticides like Chlorothion, Malathion, Parathion, and nerve gas agents.

How do organophosphates affect AChE activity?

Organophosphates irreversibly inhibit the enzyme AChE, leading to increased acetylcholine (ACh) levels in organs and tissues.

What are the signs and symptoms of organophosphate poisoning?

Patients with organophosphate poisoning will show clinical features of elevated ACh, including:

• Muscarinic Receptor stimulation effects: diarrhea, urination, miosis, bronchospasm, bradycardia, emesis, lacrimation, sweating, salivation.

• Nicotinic R stimulation effect: neuromuscular blockade and skeletal muscle paralysis.

• CNS effects: respiratory depression, lethargy, seizures, and coma.

What role does nitric oxide (NO) play in the parasympathetic nervous system (PSNS) regarding vascular smooth muscle?

Nitric oxide-containing nerve fibers in the PSNS induce vascular smooth muscle relaxation.

How can acetylcholine (ACh) influence nitric oxide release in the PSNS?

ACh binding to muscarinic receptors can also induce similar nitric oxide release in this and other tissues.

Where is nitric oxide found in the parasympathetic nervous system?

Nitric oxide is found in certain nonadrenergic noncholinergic (NANC) fibers of the PSNS that innervate the erectile tissues of the penis.

What happens when parasympathetic nerves to erectile tissue are stimulated?

Stimulation of these nerves causes the release of nitric oxide (NO) as a neurotransmitter, leading to stimulation of guanylyl cyclase and cGMP production.

What is the outcome of increased cGMP production in the erectile tissue?

Increased cGMP production leads to smooth muscle relaxation and penile erection.

What is meant by adrenergic and noradrenergic?

Adrenergic refers to a nerve ending that releases norepinephrine as the primary transmitter, while noradrenergic refers to a synapse in which norepinephrine is the primary transmitter.

What is an adrenoceptor or adrenergic receptor?

An adrenoceptor, or adrenergic receptor, is a receptor that binds and is activated by one of the catecholamine transmitters or hormones (norepinephrine, epinephrine, dopamine) and related drugs.

What is the baroreceptor reflex?

The baroreceptor reflex is the homeostatic mechanism that maintains a constant mean arterial blood pressure.

What does cholinergic refer to?

Cholinergic refers to a nerve ending that releases acetylcholine; also, it describes a synapse in which the primary transmitter is acetylcholine.

What is a cholinoceptor or cholinergic receptor?

A cholinoceptor, or cholinergic receptor, is a receptor that binds and is activated by acetylcholine and related drugs.

What does dopaminergic mean?

Dopaminergic describes a nerve ending that releases dopamine as the primary transmitter; it also refers to a synapse in which dopamine is the primary transmitter.

What is the nonadrenergic, noncholinergic (NANC) system?

The nonadrenergic, noncholinergic (NANC) system consists of nerve fibers associated with autonomic nerves that release any transmitter other than norepinephrine or acetylcholine.

What are the two main parts of the autonomic nervous system?

The two main parts of the autonomic nervous system are the sympathetic, originating in the thoracic and lumbar parts of the spinal cord, and the parasympathetic, originating in the cranial nerves and the sacral part of the spinal cord.

What is a postsynaptic receptor?

A postsynaptic receptor is a receptor located on the distal side of a synapse, for example, on a postganglionic neuron or an autonomic effector cell.

What is a presynaptic receptor?

A presynaptic receptor is a receptor located on the nerve ending from which the transmitter is released into the synapse; it modulates the release of the transmitter.