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Chapter 4: Problem 20

Using the answer code on the right, indicate which type of efferent output is being described: ___ 1. composed of two-neuron chains ___ 2. innervates cardiac muscle, smooth muscle, and glands ___ 3. innervates skeletal muscle ___ 4. consists of the axons of motor neurons ___ 5. exerts either an excitatory or an inhibitory effect on its effector organs ___ 6. dually innervates its effector organs ___ 7. exerts only an excitatory effect on its effector organs (a) characteristic of the somatic nervous system (b) characteristic of the autonomic nervous system

Short Answer

Expert verified
1-b, 2-b, 3-a, 4-a, 5-b, 6-b, 7-a

Step by step solution

01

Title - Understand the question

Identify the characteristics given in the question and understand that you need to match them with either the somatic nervous system or the autonomic nervous system.
02

Title - Identify the first characteristic

1. Composed of two-neuron chains: The autonomic nervous system (ANS) is composed of two-neuron chains (a preganglionic neuron and a postganglionic neuron). Thus, the answer is (b).
03

Title - Identify the second characteristic

2. Innervates cardiac muscle, smooth muscle, and glands: The ANS innervates cardiac muscle, smooth muscle, and glands. Therefore, it is (b).
04

Title - Identify the third characteristic

3. Innervates skeletal muscle: The somatic nervous system (SNS) innervates skeletal muscle. Hence, the answer is (a).
05

Title - Identify the fourth characteristic

4. Consists of the axons of motor neurons: The SNS consists of the axons of motor neurons. Thus, the answer is (a).
06

Title - Identify the fifth characteristic

5. Exerts either an excitatory or an inhibitory effect on its effector organs: The ANS can exert either an excitatory or an inhibitory effect depending on the neurotransmitters and receptor types. Consequently, it is (b).
07

Title - Identify the sixth characteristic

6. Dually innervates its effector organs: The ANS dually innervates its effector organs through sympathetic and parasympathetic divisions. Thus, it is (b).
08

Title - Identify the seventh characteristic

7. Exerts only an excitatory effect on its effector organs: The SNS only exerts an excitatory effect on skeletal muscles. Hence, the answer is (a).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Somatic Nervous System
The somatic nervous system (SNS) controls voluntary body movements. It innervates skeletal muscles, allowing us to perform actions like walking, grabbing objects, and speaking.

When a signal is sent through the SNS, it consists of a single neuron projecting directly from the central nervous system (CNS) to the skeletal muscle.
This neuron releases the neurotransmitter acetylcholine (ACh), which always has an excitatory effect on the muscle, causing it to contract.

Key features of the SNS:
  • Controls voluntary movements
  • Innervates skeletal muscles
  • Uses single-neuron chains
  • Always excitatory
Autonomic Nervous System
The autonomic nervous system (ANS) controls involuntary functions in the body. It regulates activities such as heartbeat, digestion, and respiratory rate by innervating cardiac muscle, smooth muscle, and glands.

The ANS is further divided into the sympathetic and parasympathetic nervous systems. It consists of two-neuron chains, with a preganglionic neuron and a postganglionic neuron.
The preganglionic neuron projects from the CNS to a ganglion, where it synapses with the postganglionic neuron, which then innervates the target organ.

Key features of the ANS:
  • Controls involuntary functions
  • Innervates cardiac muscle, smooth muscle, and glands
  • Uses two-neuron chains
  • Can be either excitatory or inhibitory
Efferent Neurons
Efferent neurons transmit signals from the CNS to the effector organs. These are the neurons that carry out the commands from the brain to the body.

In the SNS, efferent neurons are motor neurons that directly project to skeletal muscles.
In the ANS, the efferent pathway involves two neurons: the preganglionic neuron and the postganglionic neuron.
The first neuron (preganglionic) is located in the CNS and projects to a ganglion, where it synapses with the second neuron (postganglionic).
The postganglionic neuron then projects to the target organ.

Key takeaways:
  • SNS efferent neurons = motor neurons
  • ANS efferent neurons = two-neuron chains
Muscle Innervation
Muscle innervation refers to the supply of nerves to muscles, enabling their movement and control.

In the SNS, innervation is straightforward with motor neurons directly innervating skeletal muscles to produce voluntary movements.
These neurons release acetylcholine, which binds to receptors on the muscle cells to trigger contraction.

In contrast, the ANS controls the innervation of cardiac muscle, smooth muscle, and glands.
This system consists of two branches - the sympathetic and parasympathetic - both of which regulate involuntary functions in different ways.

Key distinctions:
  • SNS = Skeletal muscle innervation
  • ANS = Cardiac and smooth muscle, and gland innervation
Excitatory and Inhibitory Effects
Neurons can have either excitatory or inhibitory effects, based on the neurotransmitters they release and the receptors they target.

In the SNS, the effect is always excitatory because acetylcholine released by motor neurons stimulates muscle contraction.

The ANS, however, can be both excitatory and inhibitory.
  • Sympathetic division: Often excites organs, preparing the body for 'fight or flight' responses (e.g., increasing heart rate).
  • Parasympathetic division: Often inhibits or slows functions, promoting 'rest and digest' activities (e.g., decreasing heart rate).

This dual effect is how the body maintains homeostasis - a state of balance and stability in bodily functions.

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Most popular questions from this chapter

Which statement correctly describes acetylcholinesterase? a. It is stored in vesicles in the terminal button. b. It combines with receptor sites on the motor end plate to bring about an end-plate potential. c. It is inhibited by organophosphates. d. It is the chemical transmitter at the neuromuscular junction. e. It paralyzes skeletal muscle by strongly binding with acetylcholine receptor sites.

All afferent information is sensory information. (True or false? )

Which statement correctly describes the sympathetic nervous system? a. It is always excitatory. b. It innervates only tissues concerned with protecting the body against challenges from the outside environment. c. It has short preganglionic and long postganglionic fibres. d. It is part of the afferent division of the peripheral nervous system. e. It is part of the somatic nervous system.

During dark adaptation, rhodopsin is gradually regenerated to increase the sensitivity of the eyes. (True or false?)

Match the following: ___ 1. layer that contains photoreceptors ___ 2. point from which optic nerve leaves retina ___ 3. forms white part of eye ___ 4. thalamic structure that processes visual input ___ 5. coloured diaphragm of muscle that controls amount of light entering eye ___ 6. contributes most to eye鈥檚 refractive ability ___ 7. supplies nutrients to lens and cornea ___ 8. produces aqueous humour ___ 9. contains vascular supply for retina and a pigment that minimizes scattering of light within eye ___ 10. has adjustable refractive ability ___ 11. portion of retina with greatest acuity ___ 12. point at which fibres from medial half of each retina cross to opposite side (a) choroid (b) aqueous humour (c) fovea (d) lateral geniculate nucleus (e) cornea (f) retina (g) lens (h) optic disc; blind spot (i) iris (j) ciliary body (k) optic chiasm
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