Parasympathetic Nervous System Effects on the Eye

The parasympathetic nervous system is part of the autonomic nervous system, responsible for "rest and digest" functions when the body is at rest or trying to restore energy. It helps regulate functions like digestion, heart rate, and urination.

Acetylcholine is the neurotransmitter used by parasympathetic nerves to communicate with target organs.

The parasympathetic nervous system is more active during periods of rest and helps to conserve energy by slowing down processes like heart rate.

Muscarinic receptors are a type of cholinergic receptor found on target organs of the parasympathetic nervous system. They are responsible for mediating parasympathetic effects.

Nicotinic receptors are another type of cholinergic receptor, found in autonomic ganglia and at the neuromuscular junction. They are involved in the transmission of nerve impulses.

Atropine is a drug that blocks the action of acetylcholine at muscarinic receptors. This can lead to dilation of the pupils, decreased secretions, and a faster heart rate.

The ciliary muscle is located in the eye. It helps to adjust the shape of the lens for focusing on objects at different distances.

Cycloplegia is the loss of accommodation. It is a condition where the eye cannot adjust to focus on objects at different distances because of the ciliary muscle becoming paralyzed.

A spasm of accommodation is a condition where the ciliary muscle contracts too much, making the lens too convex, and causing difficulty seeing far objects.

The nicotinic receptor at the neuromuscular junction (NMJ) is specifically involved in the transmission of nerve impulses from motor neurons to skeletal muscles, causing muscle contraction.

Acetylcholinesterase (AChE) is an enzyme that breaks down acetylcholine in the synaptic cleft, ending its action.

Drugs that act on the parasympathetic nervous system by stimulating acetylcholine are called cholinergic drugs.

Drugs that block the actions of acetylcholine, effectively counteracting the parasympathetic nervous system are called anticholinergic drugs.

Pseudocholinesterase is an enzyme that can also break down acetylcholine, but it is more widespread in the body than acetylcholinesterase.

Cholinergic transmission refers to the process of communication between nerve cells using acetylcholine as the neurotransmitter.

Somatic motor neurons are responsible for transmitting nerve impulses to skeletal muscles, resulting in voluntary movement.

The sympathetic nervous system, also part of the autonomic nervous system, is responsible for "fight or flight" responses, preparing the body for stressful situations.

Norepinephrine is a neurotransmitter used by sympathetic nerves, primarily involved in "fight or flight" responses, causing an increase in heart rate, blood pressure, and alertness.

Adrenergic receptors are found on target organs of the sympathetic nervous system. They respond to norepinephrine and other neurotransmitters like epinephrine.

The adrenal medulla is part of the adrenal gland, which releases hormones, including epinephrine and norepinephrine, supporting the sympathetic nervous system's functions.

The sympathetic nervous system is responsible for increasing the heart rate and force of contraction, preparing the body for physical exertion.

The parasympathetic nervous system is responsible for decreasing the heart rate and force of contraction, promoting relaxation and rest.

The parasympathetic nervous system stimulates increased secretions from glands like salivary glands, lacrimal glands, and digestive glands.

The parasympathetic nervous system stimulates increased motility of the digestive system, aiding in digestion.

The parasympathetic nervous system promotes relaxation of the bladder sphincter and contraction of the bladder muscles, leading to urination.

The parasympathetic nervous system stimulates contraction of the bronchioles, constricting the airways.

The parasympathetic nervous system is responsible for constricting the pupil of the eye, reducing the amount of light that enters.

Afferent neurons transmit sensory information from the body to the central nervous system (CNS).

Efferent neurons transmit motor commands from the CNS to muscles and glands.