PSB 3002 -- Biological Bases of Behavior -- EXAM 4

vestibular sacs

- respond to gravity
- inform the brain of the head's position
- utricle
- sacule

utricle

hair cells on FLOOR

sacule

hair cells on WALL

semicircular canals

- respond to ANGULAR ACCELERATION of the head
- respond WEAKLY to change in position or LINEAR acceleration
- endolymph fluid
- Ampulla

ampulla

contains cupua, where hair cells are embedded

2 SENSORY components of vestibular system

1. vestibular sacs
2. semicircular canals

info that is conveyed to the brain by various components of the vest. system

1. head orientation (vestibular sacs)
2. angular acceleration (semicircular canals)

How is the movement of the head (angular acceleration) translated into action potentials that convey information to the brain

1. The semicircular canals are divided into sagittal, transverse, and horizontal divisions, each containing specialized receptors

2. When the head spins, the endolymph (fluid within these canals) at first resists movements when the head rotates

3. This resistance exerts force against the cupula, where hair cells are embedded, which opens mechanical channels generating a receptor potential that will be sent down the axons of the ampullary verve to the brain

4. The change in speed of the head will be determined based off of which cilia of the divisions are activated and how quickly the endolymph is moving

How is information about head position is conveyed to the brain

1. In the vestibular sacs, cilia are embedded in a gelatin mass containing otoconia

2. When the light shifts orientation the weight of the otoconia causes the gelatin to shift

3. This movement causes the cilia to shear open and TRPA1 mechanical channels to produce a receptor potential

otoconia

tiny calcium carbonate stones

What do the otoconia do?

As the orientation of the head changes, their weight causes the gelatin mass of the vestibular sacs to shift, which bends hair cells to create a receptor potential

What information is relayed to the brain by the Utricle and the Saccule?

orientation of the head

vestibular pathways

1. In the vestibular nerve, cell bodies originate in the vestibular ganglion

2. The vestibular nerve projects to the cerebellum and vestibular nuclei in the medulla

3. From the vestibular nuclei in the medulla, afferent axons project to the cerebellum, spinal cord, pons, brainstem and cranial nerve nuclei, and the temporal cortex

cutaneous

body surface

proprioception

body location in space

kinesthesia

movement of body through space

organic senses

information from, in, and around internal organs

4 encapsulated receptors

1. Merkels disk
2. Ruffini corpuscles
3. Meissner's corpuscles
4. Pacinian corpuscles

Merkels disks

form

roughness

Ruffini corpuscles

static force

Meissner's corpuscles

edge contours

Pacinian corpuscles

vibrations

How does a tactile stimulus generate a receptor potential?

1. touch detected by mechanoreceptors
2. dendrite movement opens ion channels

what stimuli generate a receptor potential?

pain & temperature

What is the name of the family of receptors that respond to temperature?

TRP (Transient Receptor Potential) Family

"nociceptors"

pain receptors

neuroanatomical pathway that mediates the sensation of TOUCH from the receptor to the primary somatosensory cortex

1. Somatosensory axons from the skin, muscles, and internal organs enter CNS via spinal nerves

2. Sensory receptors in the face and head enter through the trigeminal nerve
- Soma are in the dorsal root ganglia and cranial nerve ganglia

3. Localized information ascend through dorsal column
- Localized information such as fine touch
- Dorsal columns of spinal cord to gracile and cuneate nuclei in lower medulla
- Cross through medial lemniscus
- Project to ventral posterior nucleus of thalamus
- Primary then secondary somatosensory cortex

Neuroanatomical pathway that mediates the sensation of PAIN

1. Spinothalamic tract

2. Cross sides in spinal cord after synapsing with neurons in s.c.

3. Project up to ventral posterior nuclei of the thalamus

4. Primary then secondary somatosensory cortex

somatotopic organization of the primary somatosensory cortex

Divided into at least 5 maps of body, each map responds to a specific sub modality of SS receptors in that part of the body

What is the principle that relates the amount of cortical territory devoted to a particular body part

The size of the cortical representation for each body part reflects the precision of motor control, so that the areas for the hands, face and tongue are disproportionately large ("Cortical Homunculus")

columnar organization as it applies to the somatosensory cortex

1. Each column is responsible for different sub modalities, i.e. one column for touch, one column for vibration, etc...

2. Cells in each column respond to specific type of stimulus

3. Fast-adapting and slow-adapting are right next to each other, both in Layer 1

slowly adapting receptors from a small region of the finger

Merkel & Ruffini

fast-adapting receptors from a small region of the finger

Meissner & Pacini

What evidence suggests that the receptive fields in the somatosensory cortex are "plastic"

Monkey Experiment -- amount of cortical tissue devoted to processing info increased due to spinning disks representation of receptive fields in cortex grew larger

5 basic qualities of taste

1. bitter
2. sour
3. sweet
4. salty
5. Umami
*Fat?

bitter

- almost universally avoided
- poisonous alkaloids are bitter

sour

- Related to acidity (H+ ion in acid solutions, but associated anion also plays a role)
- Causes avoidance reaction

sweet

food detectors for safety

salty

- detects sodium chloride
- important to ingest sodium in the presence of blood loss

umami

detects (MSG) glutamate, thus may detect proteins

*fat

- Many species prefer high fat foods
- Detection may not be based on taste but rather odor and texture - But lingual lipase breaks down fatty acids. FAs may be detected by receptors in mouth

structure of papilla

1. On the surface of tongue, contains most of taste buds. Oval body with supporting cells, gustatory receptor cells, and basal cells.

2. About 10,000 on tongue, palate, pharynx, larynx

3. Fungiform:
- anterior 2/3 of tongue
- contains up to 8 taste buds
- receptors for pressure, touch, temp.

4. Foliate:
- folds ALONG back edge of tongue
- 1,300 taste buds

5. Circumvallate:
- arranged in inverted V on posterior 1/3 of tongue
- contains 250 taste buds
- plateaus surrounded by moat-like trenches

fungiform papillae

- anterior 2/3 of tongue
- contains up to 8 taste buds
- receptors for pressure, touch, temp.

foliate papillae

- folds ALONG back edge of tongue
- 1,300 taste buds

circumvallate papillae

- arranged in inverted V on posterior 1/3 of tongue
- contains 250 taste buds
- plateaus surrounded by moat-like trenches

How do taste cells come in contact with taste molecules?

1. Cilia at the end of each receptor cell project thru pore into saliva
2. Receptors synapse onto dendrites of bipolar cells
3. Bipolar cells project through 7,9,10 cranial nerves
4. Receptor cells release ATP as a neurotransmitter

neuroanatomical pathways conveying gustatory information from the mouth to the primary gustatory cortex

Anterior tongue
- Travels through chorda tympani
- Branch of 7th cranial nerve (facial)

Posterior tongue
- Send information to lingual branch of 9th cranial nerve (glossopharyngeal)

Palate and epiglottis
- 10th cranial nerve (vagus)

Which cranial nerves convey taste information to the brain

7,9, and 10 convey info to brain

the synapses located along the the way to the primary gustatory cortex

nucleus of the solitary tract --> ventral posteromedial thalamic nuclei --> primary gustatory cortex --> secondary gustatory cortex

Is the neuroanatomical conveying gustatory information from the mouth to the primary gustatory cortex pathway ipsilateral or contralateral

ipsilateral

Where else is gustatory information sent

Amygdala, hypothalamus, and adjacent basal forebrain.

What taste-related functions are mediated by the amygdala, hypothalamus, and adjacent basal forebrain?

AHB, sweet and salty
- function to reinforce effects of sweet and salty

olfactory receptor cells

- they are bipolar cells
- cell body in mucosa
- one process in mucus, divides into 10-20 cilia which contain receptors
- axons from the cell bundle together and are MYELINATED

** looks like a broom with the myelinated sheath like the broomstick

where are olfactory receptor cells

in olfactory epithelium

olfactory glomeruli

Pit stops from the nose to the olfactory cortex, located in olfactory bulb of the brain

how the inputs to the glomeruli are organized

1. Each odor activates a different pattern of glomeruli (chemical recognition becomes spatial recognition)
2. Send output to olfactory tract
3. Each receptor cell sends a SINGLE AXON into the olfactory bulb, synapse with MITRAL CELLS 4. The receptors for a given odor all link up to a glomerulus that processes that given odor

neuroanatomical pathway conveying olfactory information from the nose to the primary olfactory cortex

1. Amygdala sends olfactory info. to hypothalamus
2. the entorhinal cortex sends to the hippocampus
3. the piriform cortex sends it to the hypothalamus and to the orbitofrontal via the dorsomedial nucleus of the thalamus

What other areas receive input from the olfactory receptor cells

- amygdala
- hypothalamus
- limbic cortex
- entorhinal cortex
- orbitofrontal cortex

how olfactory stimuli are transduced in olfactory receptor cells

1. Odorant binds to olfactory receptor
2. Causes G proteins to DEpolarize receptors
3. G protein activates enzyme
4. Synthesis of cAMP
5. Opens Na channels
6. DEpolarizes olfactory cell (receptor potential)

*OGE, cAMP

Explain the statement "olfactory recognition is based on spatial recognition."

In olfactory glomeruli, each odor binds to more than one receptor and activates a specific pattern of glomeruli (chemical recognition becomes spatial recognition)

extrafusal fibers

- muscle fibers outside of a muscle spindle
- contraction provides motive force
- served by axons of alpha motor neurons

motor unit

- A motor neuron and all of the muscle fibers it innervates
- A motor neuron, axon, and extrafusal fibe

neuromuscular junction

synapse between efferent's terminal and muscle fiber

motor end plate intrafusal muscle fibers

- sensory organs
- STRETCHED when muscle LENGTHENS
- RELAXED when muscle SHORTENS
- respond to muscle length
innervated by Gamma motor neuron

muscle spindle

- Stretch receptor (sensory) in intrafusal fibers
- Detect muscle length

alpha motor neuron

Innervate extrafusal fibers and initiate contraction

gamma motor neurons

- Innervates INTRAfusal muscles
- Shortening increases sensitivity of muscle length
- INsensitive to stretch when relaxed
- Helps regulate length of entire muscle

Golgi tendon organ

- Stretch receptors
- Code stretch by RATE of FIRING
- Respond to how hard a muscle is pulling

motor homunculus

- Somatotopically organized
- The more intricate the movements, the more space lent to by the motor cortex
**e.g., fingers/thumbs have way more real estate on the cortex than the genitals/trunk

dorsal horn

receives sensory info in spinal cord (afferent)

ventral horn

sends motor output to skeletal muscle (efferent)

ventral funiculus

- Transmits corticospinal, vestibulospinal, reticulospinal, and tectospinal tracts
- ventral: CVRT
- White matter

dorsal funiculus

- Transmits f. cuneatus and f. gracilis tracts
- Dorsal: FCFG
- white matter

monosynaptic stretch reflex

A reflex in which a muscle contracts in response to its being quickly stretched; involves a sensory neuron and a motor neuron, with one synapse between them.

Golgi tendon organ reflex

1. tension on tendon activates sensory neuron
2. sensory neuron stimulates interneuron
3. interneuron inhibits motoneuron
4. tension on tendon is reduced

-determines if the muscle is too contracted
--never monosynaptic bc it has to work through an inhibitory neuron

somatotopic organization of motor neurons in the spinal cord

- motor homunculus
- the activation of neurons located in particular parts of the primary motor cortex causes movements of particular parts of the body.

*organized in terms of movements

origin of Dorsolateral pathway (to dorsolateral motor neurons)

red nucleus

course of Dorsolateral pathway (to dorsolateral motor neurons)

Rubrospinal & Rubrobulbar Tracts descend on contralateral side in dorsolateral funiculus

terminations of Dorsolateral pathway (to dorsolateral motor neurons)

- more focused termination (contralaterally)
- Interneurons + Dorsolateral motor neurons innervating DISTAL LIMBS

origin of Ventromedial pathway (to medial motor neurons)

- Vestibular nuclei(balance),
- Tectum(orienting), and Reticular Formation(posture)

course of Ventromedial pathway (to medial motor neurons)

Vestibulospinal, tectospinal, and reticulospinal tracts all descend ipsilaterally in VENTRAL FUNICULUS (EXCEPT TECTOSPINAL)

terminations of Ventromedial pathway (to medial motor neurons)

- Widespread (Bilaterally)
- Interneurons + Medial motor neurons innervating AXIAL AND GIRDLE MUSCULATURE

origin of the LATERAL corticospinal tract

cortical neurons

course of the LATERAL corticospinal tract

Decussates (cross) at caudal medulla and descends contralaterally

terminations of the LATERAL corticospinal tract

innervates motor neurons controlling DISTAL LIMBS

origin of VENTRAL (ANTERIOR) corticospinal tract

cortical neurons

course of VENTRAL (ANTERIOR) corticospinal tract

axons descend ipsilaterally

terminations of VENTRAL (ANTERIOR) corticospinal tract

Splits to both sides of spinal cord onto motor neurons innervating upper legs and trunk

What cortical areas provide direct inputs to the motor cortex

Supplementary motor area(SMA) + Premotor Cortex: involved in planning movements, execute plans via primary motor cortex, active when people execute or think about sequences of movements, receive inputs from association areas in parietal and temporal lobe

supplementary motor area

*behavioral sequences + spontaneous movement
*stimulation results in a desire to move

premotor cortex

* initiation of behavior

mesencephalic locomotor region

- Initiation/control of locomotor movements
- Subcortical structure

where is the mesencephalic locomotor region

ventral to inferior colliculus

effect of stimulating the mesencephalic locomotor region

stimulation induces pacing movements in cats

Why is the flocculonodular lobe of the cerebellum sometimes referred to as the "vestibulocerebellum"?

it receives input from vestibular system + projects to vestibular nucleus

Where do the output structures of the basal ganglia project?

VA/VL Thalamus + Cortex

Explain the following statement: "The basal ganglia control movement by disinhibition."

* Disinhibiting direct pathway by inhibiting output structures
* Brain is normally inhibited.
- Motor (VA/VL) thalamus is tonically INHIBITED by Basal Ganglia structures (GPi/SNpr) Via GABA
- Direct pathway activated (inhibitory pathway)
1. Motor cortex EXCITES Striatum
2. Striatum INHIBITS GPi
3. GPi, which normally INHIBITS Thalamus, is INHIBITED ITSELF, which allows the Motor (VA/VL) thalamus to send EXCITATORY MESSAGES to MOTOR CORTEX

neurological basis for Parkinsonism

1. Caused by damage to nigrostriatal bundle
- Disrupts balance between direct and indirect pathways

2. Excitatory zone of caudate-putamen
- D1 receptors (excitatory)
- Sends axons to GPi

3. Inhibitory zone of caudate-putamen
- D2 receptors are inhibitory
- Send axons to GPe

4. Net result of activation of both is excitatory

5. Effect of damage to the substantia nigra
- Loss of activation
- Decrease in inhibitory output to the ventromedial system may underlie muscular rigidity and poor postural control

neurological basis for Huntington's Disease

1. Inhibitory GABA neurons die first
- Increases activity of GPe which inhibits subthalamic nucleus

2. Decreases GPi activity

3. Excessive movement

4. Later, virtually all neurons in caudate and putamen die resulting in immobility