chapter 11

Explain the significance of the vagus nerve in the autonomic response

- Contains about 75% of all parasympathetic fibers - Sensory information from internal organs to brain - Output from brain to organs

State 5 actions of the sympathetic nervous system

- Functions of sympathetic NS: Sympathetic NS: "fight or flight" Prepare the body for intense physical activity such as in emergencies Wide range of actions throughout body: •increase heart rate, •increase pulmonary airflow (bronchodilation) •redirect blood to vital areas e.g. muscles & lungs (& away from intestines, skin etc) •inhibit digestive system (decreased peristalsis) •increase blood glucose concentration •increased metabolism Generally activated as a whole (mass activation)

Describe the transmission of a neural signal at a neuromuscular junction

- Presynaptic axon terminal filled with synaptic vesicles and mitochondria

Describe the structure of the neuromuscular junction.

- Presynaptic axon terminal filled with synaptic vesicles and mitochondria - Synaptic cleft - Postsynaptic membrane of the skeletal muscle fiber

What is a varicosity in the autonomic nervous system?

A series of swollen ends that act as synapses

n the autonomic nervous system, neurotransmitter activation of its receptor terminates when the neurotransmitter is metabolized by enzymes in the extracellular fluid, or when it diffuses away. Which other mechanism leads to termination of neurotransmitter activity?

Active transport into surrounding cells

What is the trigger for ACh release into the synaptic cleft of a neuromuscular junction?

An action potential at the axon terminal opens voltage-gated Ca2+ channels.

Explain dual innervations and control

Dual Innervation: •Most visceral organs receive both sympathetic & parasympathetic innervation •Both divisions do not normally innervate an organ equally Effects may be: •antagonistic •co-operative

State 5 actions of the parasympathetic nervous system

Functions of parasympathetic nervous system: Parasympathetic NS: "rest & digest" Broadly opposite to the sympathetic nervous system: •decrease in heart rate •decrease in pulmonary flow (bronchoconstriction) •redirect blood to digestive system & away from skeletal muscles etc •penile erection •increased glandular secretion (nasal, lacrimal, salivary) •increased peristalsis and digestive enzyme activity •relaxation of gut sphincters Localized responses, not mass activation

Why is the parasympathetic nervous system also called the cranio-sacral division?

Its nerves arise in the head and sacrum.

What is the main enzyme responsible for the breakdown of catecholamines?

Monoamine oxidase

What would be the effect of ACh binding to its receptor on the postsynaptic muscle cell?

Na+ would flow into the cell and K+ would flow out of the cell.

Which of these characteristics is the same in both the sympathetic and parasympathetic branches for the vast majority of neurons?

Preganglionic neurotransmitter

Neurons in the parasympathetic pathway use which of the following neurotransmitters?

acetylcholine

Somatic motor neurons secrete the neurotransmitter ________ onto ________ receptors at the target tissue.

acetylcholine; nicotinic

The division of the efferent nervous system that controls smooth and cardiac muscles and many glands is the ________ division.

autonomic

Which of the following best describes the direction and function of efferent signals?

away from the central nervous system, cause motor effects in glands or muscles

Describe the physiological role of the autonomic division and its branches.

controls involuntary effectors - smooth, cardiac and glandular cells (endocrine and exocrine) - Targets lungs, heart, digestive, urinary and reproductive systems, blood vessels, sweat glands, piloerector muscles. - Critical for homeostasis

The neurotransmitter that controls skeletal muscle causes which of the following?

muscle contraction

Which type of receptor is found in the neuromuscular junction?

nicotinic

What type of acetylcholine receptor is present in the postganglionic neurons and on the target tissue in autonomic pathways?

nicotinic on the postganglionic neurons and muscarinic on the target tissue

The target tissue(s) of somatic motor neurons is/are ________.

skeletal muscle

Which of the following are components of the efferent nervous system?

sympathetic neurons parasympathetic neurons somatic motor neurons

Which nervous system division has parasympathetic and sympathetic branches?

the autonomic division of the efferent nervous system

Sympathetic pathways originate in which region of the spinal cord?

thoracic and lumbar

Compare and contrast the anatomy and chemical communication of the somatic to the sympathetic and parasympathetic branches

• Most internal organs are under antagonistic control - One autonomic branch is excitatory, and the other branch is inhibitory

Describe the structure and secretions of the adrenal medulla.

• Primary neurohormone is epinephrine - Secreted into the blood - In the adrenal cortex