BIOL 1412 Nervous system IV

LECTURE 6

What are the effectors of the ANS?

Smooth and cardiac muscles, glands

What 2 neurons are involved to the effector in the ANS?

Preganglionic + postganglionic

How can ANS neurons be distinguished by?

Type of nt released

What 2 types of nt distinguish ANS neurons?

Cholinergic + adrenergic

Cholinergic refers to which nt?

ACh (Acetylcholine)

Adrenergic refers to which nt?

Norepinephrine (NE)

What are the 2 subdivisions of the ANS?

Sympathetic + parasympathetic

What is the function of the sympathetic NS?

Prepares the body for activity

What is the “response” of the sympathetic NS?

Fight or flight

When is the sympathetic NS activated?

During exercise

In the SNS, axons exit the CNS via what?

Spinal nerves

At a ganglion involved with the SNS, which nt is involved?

ACh

At the effector involved with the SNS, which nt is involved?

NE

As an exception, what nt is present at the effector involved with the SNS if it is a gland?

ACh (instead of NE)

In the SNS, how must a chemical stimulation of a postsynaptic cell be stopped?

Nt must be broken down or removed

To stop chemical stimulation of a postsynaptic cell, ACh must be broken down by what enzyme?

Acetylcholinesterase (AChE)

On what surface must ACh be broken down by AChE?

Postsynaptic membrane

What IS a postsynaptic membrane made of?

Cell body/dendrites of postganglionic neuron (or effector cell)

Once ACh is broken down by AChE, where is there a NE reuptake?

At presynaptic membrane

Once there is an NE reuptake at the presynaptic membrane, it is then broken down by what enzyme?

Monoamine oxidase (MAO)

What is the function of the parasympathetic NS?

Rest & digest

What subdivision of the NS does “housekeeping” refer to?

Parasympathetic NS

Where are cell bodies involved with the parasympathetic NS located?

In brain stem or sacral spinal cord

In the parasympathetic NS, the nt at the ganglion cell AND effector is the same. This nt is?

ACh

Where do most organs controlled by ANS receive input from?

Both SNS and PSNS

Most organs controlled by ANS, receiving input from both SNS and PSNS usually have _______ actions

“opposite”

ANS regulates internal processes continuously and ___________.

“automatically”

With the example of heart rate, which (SNS/PSNS) excites/inhibits?

SNS = excites

PSNS = inhibits

With the example of GI tract motility, which (SNS/PSNS) excites/inhibits?

SNS = inhibits

PSNS = excites

Which (SNS/PSNS) causes pupils of eyes to dilate/constrict?

SNS = dilate

PSNS = constrict

Which (SNS/PSNS) causes heart rate to increase + force of contraction?

SNS

If SNS increases heart rate (HR), what would PSNS do?

Decrease HR

As for the gastrointestinal tract (GI Tract), which (SNS/PSNS) increases/decreases motility?

SNS = decreases

PSNS = increases

Blood vessels are made of ______ muscle.

“smooth”

Which (SNS/PSNS) cause blood vessels to vasoconstrict (make it smaller so blood flows faster)?

SNS

The PSNS does not innervate blood vessels, except for what 2 places?

Erectile tissues

Which (SNS/PSNS) cause sweat gland secretion (hint: one of which has no innervation)?

SNS

Which (SNS/PSNS) causes digestive glands to increase/decrease secretion?

SNS = decrease

PSNS = increase

Which (SNS/PSNS) causes ejaculation?

SNS

Which (SNS/PSNS) causes erection and lubrication?

PSNS

SNS decrease secretion in the digestive glands, except for?

Saliva

T/F: Does the hypothalamus need cerebral input for its ANS functions?

No, but emotions can cause autonomic effects

What are 4 given examples of emotions that can cause autonomic effects?

Blushing, fainting, cold sweat, ⬆HR

What is the path of the higher control of ANS (cerebrum → ? → ? → ?)?

Cerebrum → hypothalamus → medulla oblongata → ANS

In the higher control path of the ANS, when the path reaches the ANS, it splits off into 2 paths towards what 2 subdivisions?

SNS + PSNS

The somatic NS transmits signals from CNS to the _______ system.

“skeletal”

In the somatic NS, to reach the effector/skeletal muscle, what neurons carry the signal from the “CNS (brain) → CNS (spinal cord),” and CNS (spinal cord) → E,” respectively?

“CNS (brain) → CNS (spinal cord)” = upper motor neuron

“CNS (spinal cord) → E” = lower motor neuron

What are the 3 types of movement in the somatic NS?

Reflexes, voluntary, rhythmic

What are the 2 types of reflexes in the somatic NS?

Spinal + postural

Which is least complex, spinal or postural reflexes?

Spinal

What do spinal reflexes require sensory input from (3)?

Sensory neurons like proprioceptors (e.g. muscle spindles) + pressure/pain receptors

Postural reflexes maintain what 2 things?

Balance + posture

What do postural reflexes require sensory input from (3)?

Like proprioceptors (e.g. muscle spindles), eyes, inner ear

Which type of movement in the somatic NS is most complex?

Voluntary movement

With voluntary movement, no ______(internal/external) stimuli is required

“external”

Walking and running are described in which of the 3 types of somatic NS movement?

Rhythmic movement

Rhythmic is a combination of what 2 movements?

Reflexive and voluntary movements

See the flip side

What are the 6 levels of motor control?

Planning (Level 1), Level 2, Level 3, Spinal Cord (Level 4), Cerebellum, Basal Nuclei

What does the (Level 1) planning level of motor control plan the sequence of?

Muscle contractions

What cortex in the brain does the (Level 1) planning level of motor control signal to?

Primary motor cortex

The (Level 1) planning level of motor control works with input from what brain region?

The cerebellum

What is unique about level 2 and 3 of motor control?

They involve descending tracts → lower motor neurons

In level 2 of motor control, signals are directly sent to lower motor neurons via what tract?

Corticospinal tract

For what purpose are signals sent directly to lower motor neurons via the corticospinal tract?

For fine skilled movements

In level 3 = ? → descending motor tracts → ?

Brainstem nuclei → descending motor tracts → lower motor neurons

In level 3, “brainstem nuclei → descending motor tracts → lower motor neurons” is a representation of ______ tracts

“indirect”

From what 3 brain parts/regions does the 3rd level of motor control receive input from?

Cortex, basal nuclei, cerebellum

The 3rd level of motor control is involved in coordination of large muscle groups for what 2 functions?

Maintenance of posture + locomotion

The 4th level of motor control is the spinal cord, which contains cell bodies of what kind of neuron?

Lower motor neurons

Level 4 (Spinal cord) of motor control contains central pattern generators (CPGs). What are these?

Network of neurons which set rhythmic, repeated movements

For central pattern generators (CPGs) to begin/stop movement, what do they require?

Cortical signals

The cerebellum has a role in planning + initiating movement by communicating with what areas?

Cortical areas

What does the cerebellum store?

Planned movement

The cerebellum stores planned movement and compares what?

Actual to plan

Where does the cerebellum use sensory input from, for example?

Proprioceptors

What 3 things does the cerebellum have a maintenance function for?

Balance, eye movements, muscle tone

What does low level of contraction mean for the cerebellum maintaining muscle tone?

There is a constant, slight contraction in your muscles even when you’re relaxed.

What 2 things does the cerebellum coordinate?

1. Skilled voluntary muscle movements

2. Timing of contractions involved >1 joint

Basal nuclei aid in _________ movement

“planning”

What does basal nuclei suppress?

Unwanted motions (e.g. at rest)

What does basal nuclei have a role in maintaining?

Muscle tone

The corticospinal (direct) pathway signals from ? → ?

Cortex → skeletal muscle

What are the 2 types of neurons involved with the corticospinal (direct) pathway?

Upper motors neurons + lower motor neurons

Where are the cell bodies of upper motor neurons located?

Primary motor cortex

Where are the axons of upper motor neurons?

Down spinal cord

Where are the cell bodies of lower motor neurons located?

Ventral horn of spinal cord

Where do the axons of lower motor neurons exit via?

Spinal nerves

What are the 2 clinical applications of the somatic NS?

1. Destruction of upper motor neurons

2. Destruction of lower motor neurons

Reflex arcs are still present in the destruction of upper motor neurons. What does this mean?

Reflex arcs between sensory and lower motor neurons are still present

What 2 results can the destruction of upper motor neurons lead to?

Spastic paralysis + exaggerated reflexes

In spastic paralysis, the presence of what increases muscle tone?

Reflex arcs

What is meant by “no muscle atrophy”, a feature of spastic paralysis?

The muscle doesn’t waste away/shrink (because constant reflexes keep it active)

What are 3 given examples of exaggerated reflexes?

Patellar, Achilles, Babinski sign

A loss of ________ signals to _____ motor neurons causes exaggerated reflexes.

“inhibitory,” “upper”

What is a strong example of a reflex that can test damage to upper motor neurons?

Plantar reflex

What does the plantar reflex entail?

Scratching the sole of ones foot

What is the Babinski sign when attempting to trigger the plantar reflex?

An extension of the big toe

A positive Babinski sign indicates damage to upper motor neurons, except at what age where it is normal?

In babies

Why is a positive Babinski sign normal in babies?

Their corticospinal tract is not yet fully myelinated