HN220 Midterm 2

What are the anatomical divisions of the nervous system?

1) Central nervous system (CNS)

2) Peripheral nervous system (PNS)

What does the CNS consist of?

brain and spinal cord

- its the integrating centre

What does PNS consist of?

All neural tissue outside the CNS

What are the 2 different neurons the PNS consists of?

1) afferent neurons

2) efferent neurons

What are afferent neurons?

Sensory neurons

-Carry information towards the CNS

What are efferent neurons?

Motor neurons

-Carry information away from the CNS

What are neurons

cells that send and receive electrical signals rapidly and over long distance if needed

The CNS is ncessary for the maintenance of _________________

homeostasis

What is cerebrospinal fluid (CSF)?

clear watery fluid bathing the CNS

Where is cerebrospinal fluid produced?

choroid plexus

- produces 400-500 mL/day

How many times is cerebrospinal fluid recycled every day

3 times

What is the function of CSF?

- cushions the brain

- maintains a stable interstitial fluid environment

How much oxygen does the brain use at rest?

20% of oxygen consumed by body

How much oxygen does the brain use at rest?

50% of oxygen consumed by body

What method do neurons depend on for oxygen?

aerobic glycolysis

True or false: there are no glycogen stores in the brain at all

False: there are some in glial cells

True or false: fatty acids are used for energy

False: they are not used for energy

True or false: ketones are used for energy during extreme conditions

true

What structure maintains the blood brain barrier

Capillaries

What are capillaries?

sites of exchange between the blood and the interstitial fluid

What are capillaries made of?

a single layer of endothelial cells

What type of transport occurs in capillaries?

diffusion

How are the capillaries in the CNS different from the capillaries in the rest of the body?

- capillaries in the CNS do not have pores

- they have tight junctions

What kind of cell junctions do the capillaries in the brain have?

TIGHT JUNCTIONS

How do hydrophilic solutes move in and out of the brain capillaries?

Carrier mediated transport

True or false: the spinal cord is continuous with the brain

true

The spinal cord is surrounded by the _______________

vertebral column

A nerve is a bundle of ____________

axons

What is a mixed nerve?

One that has both efferent and afferent neurons

- carries both sensory and motor information

What is a dermatome?

specific segment of skin supplied by a single spinal nerve

What are two functional parts of gray matter?

dorsal and ventral

What are dorsal roots?

sensory input to spinal cord

- afferent

What are ventral roots?

motor output from spinal cord

- efferent

True or false: spinal nerves are not mixed

false: they are mixed

White matter forms ______________

tracts (ascending and descending)

What are ascending tracts?

tracts that conduct impulses to the brain

- sensory, dorsal tracts

What are descending tracts?

tracts conduct impulses down the cord away from the brain

- motor, ventral

What are reflexes?

Automatic patterned responses to certain stimuli

What is the reflex arc?

1) sensory receptor

2) afferent neuron

3) integration center

4) efferent neuron

5) effector organ

What are the 3 different reflexes?

1) stretch reflex

2) withdrawal reflex

3) crossed extensor reflex

What is the muscle spindle stretch reflex?

a tap on the knee's tendon causes a change in the muscle fibre length in your quads

Explain the communication between the afferent and efferent neurons during the muscle spindle stretch reflex

- spindles detect the change in muscle fibre length and send afferent information to the spinal cord

- theres a direct excitatory connection with efferent neurons and then this response innervates the quads to extend your knee and (the kick)

true or false: the muscle spindle stretch reflex is a monosynaptic reflex

true

What does the muscle spindle stretch reflex do to the hamstrings?

inhibits it using inhibitory neurons

- decreases its activity

- allows for knee to contract

Explain the withdrawal reflex

1) Leg in pain: Stimulation of the afferent fibers causes excitatory stimulus in the hamstrings and inhibitory stimulus in the quads (reciprocal innervation)

Other leg: Excitatory neurons on quads, and inhibitory neurons on hamstrings (allows you to balanc)

2) efferent neurons cause knee flexion

What is perception

- Conscious interpretation of the world based on sensory systems, memory, and other neural processes

True or False

We perceive info solely based on the effector responses that occur due to afferent/sensory responses

False

We perceive info is a combo of previous experiences (memories) and effector responses that occur

What are some senses that are associated with the skin

Touch, pressure, temperature

What is proprioception

Perception of limb and body positions

What are examples of special senses

-Balance + equilibrium

-Vision

-Hearing

-Taste

-Smell

Sensory neurons have sensory ______

Sensory receptors

What do sensory receptors detect

Detect specific form of E in the external environment

What are some examples of modality

-Light

-Sound

-Pressure

-Temperature

-Chemicals

What is the Law of Specific Nerve Energies

A given sensory receptor is specific for each modality

Ex. Thermoreceptors are sensitive to their specific modality (temp)

Sensory receptors require an adequate ________, which leads to depolarization of that particular type of neuron

Adequate stimulus

What is sensory transduction

Conversion of stimulus E into electrical E

What are receptor/generator potentials

-Similar to a graded potential

-Opening or closing of ion channels

-Triggered by sensory stimuli

If a receptor potential exceeds threshold, it can generate an ___ _______

action potential

How do specialized nerve endings work

Swelling at dendritic end which forms at the sensory receptor end

Pressure at the end opens mechanically gated channel

What is receptor adaptation

-Decrease in amplitude of receptor potential over time in the presence of a constant stimulus

-Corresponding decrease in frequency of action potentials

-Decreases perception of stimulus

What's the difference between slowly adapting receptors and rapidly adapting receptors

-Rapidly adapting receptors respond only at the moment when the stimulus is applied

-Slowly adapting receptors continue to respond as long as the stimulus is applied

What are labelled lines

-Specific neural pathways transmitting information of a specific modality

What is a sensory unit

-Single afferent neuron, plus all receptors associated with it

What is a receptive field

Area in which a sensory unit is activated

Touching anywhere within a receptive field activates the __________ _________

sensory neuron

Explain the generalized pathway for sensory systems

-Stimulus picked up receptors and travels to spinal cord or brain stem via afferent neuron (1st order)

-Travels to thalamus via 2nd order neuron

Travels to cortex via 3rd order neuron

What are the 3 factors of sensory coding

-Stimulus type

-Stimulus intensity

-Stimulus location

Describe stimulus type as a factor of sensory coding

Combination of receptor type and pathway activated

True or False

If you increase the stimulus,

AP frequency increases

# of receptors activated increases

True

What is acuity

Precision with which a stimulus is perceived

What is 2 point discrimination

Two-point discrimination is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one

In large receptive fields, 2 stimuli within close distances of each other are often perceived as _______

One point

Smaller 2-point discrimination distances indicate greater ________ ________

Greater tactile acuity

What body region has the greatest tactile acuity

Lips

What body region has the lowest tactile acuity

Calf

What is pain perception

Sensation produced by potentially tissue damaging stimulus

What is involved in the pain response

-Activation of nociceptors

-Autonomic responses (sweating)

-Emotional responses (fear)

-Reflexive withdrawal

True or False

Pain perception depends on past experiences

True

Ex. Big pain at dentist when little, little pain at dentist when big= big pain

What is visceral pain

- Pain originating in internal organs (not limited to body surface)

What is referred pain

Sensation referred to body surface

Ex. Heart attack victim complains of pain in left side of chest, not heart

Why does referred pain occur

Nociceptors are following along a similar neural tract to cerebral cortex as other parts of our body

True or False

Signals can be modulated as they transmit along sensory pathways

True

What's a specific example of how pain can be modulated as it transmits along a sensory pathway

Gate control theory

What is the gate control theory?

Non-painful sensations can override and reduce painful sensations

If you rub your toe after you stub it, it'll hurt less

How does gate control theory work

Many nociceptors share synapses with interneurons and communication can occur

These interneurons are inhibitory interneurons, so activating them will communicate with 2nd order neurons, which will dull the pain perception

What are 2 parts of the Peripheral Nervous System

1. somatic nervous system

2. autonomic nervous system

What is the somatic nervous system?

Controls voluntary movement

- controls skeletal muscle

What is the autonomic nervous system?

Controls involuntary movement

- controls smooth muscle, cardiac muscle glands, and adipose tissue

What other systems does the autonomic nervous system work with to maintain homeostasis?

1) endocrine system

2) behavioural state system

What are the two parts of the Autonomic Nervous System (ANS)?

1) sympathetic

2) parasympathetic

What is the sympathetic nervous system?

fight or flight

What is the parasympathetic nervous system?

rest and digest

True or false: if one part of ANS is working the other is not

false: the sympathetic and parasympathetic nervous systems work together, so one may be more active than the other, but they are both always working

True or false: the parasympathetic nervous system innervates more effector organs than the sympathetic nervous system

false: both divisions of the autonomic nervous system innervate most effector organs

- known as dual innervation

What is the primary function of the dual innervation by the ANS

regulate organs to maintain homeostasis

Parasympathetic and sympathetic activities tend to be _________________

antagonistic

What parts of the brain initiate autonomic, endocrine, and behavioural responses?

1) hypothalamus

2) pons

3) medualla

How does the ANS work with the endocrine system to maintain homeostasis?

- sensory information goes to the homeostatic control centres (hypothalamus, pons, medulla)

- the centres monitor and regulate bodily functions

(blood pressure, temperature control, and water balance)

What is the "centre for homeostasis"?

hypothalamus

What are the different kinds of motor outputs from the integrating centres

1) autonomic

2) endocrine

3) behavioural