Behavioral Neuroscience Exam 2

8 Senses

Touch

Taste

Smell

See

Hear

Movement

Balance

Interception

Somatic Sensory Info

The sensations we get from the skin, muscles, bones, and joints.

Visceral Sensory Info

The sensations from viscera ( i.e internal organs)

Somatic Sensory

Sensations can be both pleasant and unpleasant.

Visceral Sensory

Sensations are always unpleasant.

Special Sensory Info

Sight, taste, smell, hearing, and equilibrium (state of balance)

Why is the “special sensory info” special?

Rely on sensory organs like the eyes, ears, nose, and tongue to detect stimuli and convert signals.

Function of Senses

Ability to make the body aware of external and internal change. In turn permitting the CNS to produce reactions and maintain body homeostasis.

Chemoreceptors

Detect change in chemicals (think taste)

Osmoreceptors

Detect change in osmotic pressure (the amount of salt to water ratio that results in things like bloating)

Thermoreceptors

Detect change in temperature

Mechanoreceptors

Detect mechanical forces (think touch/pressure)

Photoreceptors

Detect light (think sight)

Nociceptors

Detect pain

Receptors

An entire cell that is specialized to respond to a physical/chemical stimulus and covert that stimulus into a neural (electrical) signal.

Hapis

Receptors for fine touch and pressure cause physical disturbances that result in the opening of sodium channels which leads to DEPOLARIZATION which in turn can lead to an ACTION POTENTIAL

Somatosensory System

Speed is determined by myelin and diameter.

Meissner’s Corpuscles

Small, oval shaped sensory receptors located in the skin. Responsible for detecting light touch, vibrations, and fine tactile sensations.

What determines the speed of a nerve impulse?

Myelin and axon diameter. The larger the diameter the faster the conduction.

Conduction

The process of an electrical signal, called an action potential, traveling down a nerve cells axon. Think domino effect: when one part of the axon is activated, it triggers the next section and so on.

A Fibers

Fast pain

C Fibers

Aching pain

Proprioceptors and Mechanoreceptors

Peripheral somatosensory axons Group 1 and 2 have the largest diameter and the thickest myelin

Peripheral somatosensory axons Group 3

Carry sharp pain or cool/cold info and are thinly myelinated (meaning covered by myelin)

Peripheral somatosensory axons Group 4

Carry dull pain, deep pain, crude touch or warm/hot information and are unmyelinated (not covered by myelin)

DCML Tract (dorsal column medial lemniscus)

The main sensory pathway for hapsis (fine touch, vibration and proprioception)

DCML Neuron Orders & Path

Involves 3 orders of neurons: 1st Order (Skin to Medulla) → 2nd Order (Medulla to Thalamus) → 3rd Order(Thalamus to Somatosensory Cortex).

DCML Decussation (Crossing Over)

The sensory information crosses the midline (decussates) at the medulla (lower brainstem). This means sensation from the right side of the body is processed by the left brain, and vice-versa.

Fast pain

Transmitted by the spinothalamic tract

Deep pain

Transmitted by the spinoreticular tract

Dorsal (Top)

Part of the spinal cord that processes sensory

Ventral (Bottom)

Part of the spinal cord that process motor cortex

Primary Somatosensory Cortex

Located in the post central Cyrus of the parietal lobe. Lies behind the primary motor cortex of the frontal lobe. This is afferent.

Afferent

Neurons that carry information from sensory receptors found all over the body towards the central nervous system

Efferent

Neurons also called motor neurons are the nerve fibers responsible for carrying signals form the brain to the PNS

Motor cortex

Located in the frontal lobe of the brain in the posterior pre central gyrus. This is efferent.

Gyrus

Ridge like elevation found on the surface of the cerebral cortex.

Apraxia

A disorder of the brain and nervous system in which a person is unable to perform tasks of movements when asked.

Posterior parietal cortex

An area of the brain associated with planning movements and spatial awareness.

Pre central gyrus

Sends commands to execute the movements. Motor cortex.

Descending motor pathways

Groups of myelinated nerve fibers that carry motor info from the brain or brain stem to muscles via the spinal cord. Left controls right, right controls left.

Motor Unit (Lower Motor Neurons)

A single spinal motor neuron and all of the individual muscle fibers it contacts.

ALS

Disease of the motor neurons in which both UMS and LMN gradually deteriorate and then die.

Lower motor units (LMN)

Found in the spinal cord (from neck to feet) or brainstem (feet)

Upper motor neurons

Originate in the cerebral cortex and travel down to the brain stem or spinal cord.

Corticobulbar tract

A neural pathway from the cerebral cortex to the brainstem, controlling voluntary movements of the face, head, and neck muscles.

The reflex

The simplest interaction between sensory and motor systems

The stretch reflex

Helps us maintain a limbs position in space against a sudden, unexpected load.

Withdrawal reflex

Touch something painful and you immediately pull away. Motor neurons fire to contract muscles based on sensory information from the skin.

Basal Ganglia

Brain structures that control muscle movements.

Substantial nigra

A part of the midbrain, located in the brainstem. Involved in movement and reward

Anosmia

Loss of sense of smell

Dysgeusia

Loss or alteration of sense of taste

Olfaction

the sense of smell is the response to chemicals that contact the membranes inside the nose

Odorants

chemicals that activate transduction processes in neuron

Cribriform plate

Thin sheet of bone through which small clusters of axons penetrate, coursing to the olfactory bulb

Glomeruli

Primary processing units for processing smell in olfactory bulb. Enable brain to spatially discriminate between many odors spatially.

Why might it be important to detect relatives’ scent?

Odor may influence mate choice to avoid genetic inbreeding

Pheromones

Secreted chemical factor that triggers a social response in members of the same species. Types include sex, alarm, and food trail.

Taste

Provides an assessment of foods. Specialized tongue receptors encode 5 distinct tastes • Salty, sour, bitter, sweet, umami

Taste buds

Tiny sensory organs that detect dissolved chemicals in food and transmit signals to brain for your perception of taste. Located in the small bumps of your tongue called papillae

Gustation

Tastants bind to corresponding receptors on taste cell • Activation of many different G proteins, which release Ca++ inside • Triggers neurotransmitter release and primary sensory fires an AP to gustatory system in brain

Gustatory cortex

A taste ”map” is preserved in the gustatory cortex like sensory and motor systems • Within the frontal lobe and contains part of the insula cortex • Involved in taste perception, flavor discrimination and taste guided behaviors

Conditioned taste aversion (CTA)

Aversive experiences with a certain food can change our evaluation of its taste.

Audition

The physical stimulus are vibrations of air molecule.

Sine waves

Smooth s shaped waveform defined by mathematical sine function. Represents an oscillation (central line) and is obsevered in sound,light, and electrical signals.

Pinna

Captures and amplify vibrations in the air. Outer visible part of the ear.

Tympanic membrane (Eardrum)

Sound waves travel down the auditory canal and impact this.

The ossicles

Three small bones on the other side of the tympanic membrane. Movement of the tympanic membrane moves the bone.

What vibrates the tympanic membrane?

Sound

What happens when sound vibrates the ossicles?

Sound causes the stapes (stirrup) to vibrate the oval window of the cochlea.

What is the cochlea?

Fluid filled spiral with inner finger like structures called the organ of corti (sense organ of audition)

Organ of corti

Convert sound vibrations into electrical signals that are transmitted to the brain for interpretation

Hair cells

Special sensory receptors of the inner ear. Modified epithelial cells that act as Mechanoreceptors.

Tonotopic maps

Regions that respond best to one particular tone will be neighbored by regions that respond best to a tone of a slightly different frequency

Medial geniculate nucleus

Region of the thalamus that processes auditory info

Primary auditory cortex location

Located within the temporal lobe of the cortex

Responsibility of the primary auditory cortex

The initial processing of auditory information including the perception of sound features like pitch, volumes, and ray themes.

Higher Order Processing

parallels with visual system

What is essential to vision?

Light - without light there can be no visual perception.

How can light be characterized?

Similar to sound, it can be characterized as a sine wave

Wavelength

Color

Amplitude

Brightness

Retina

Contains the sense organs for vision. Its where the physical stimulus is converted into a neural signal

Where does light enter through?

The pupil - the iris’s dictates the opening of the pupil and in bright light the pupil constricts and in dim light the pupil dialates

What nervous system leads to pupil dilation?

Sympathetic

What nervous system leads to pupil constriction?

Parasympathetic

Sensitivity

The larger the pupil size, the more light permitted in

Acuity

In bright light, the pupil constricts. This way you can see things sharper

Lens

Focuses incoming light (permitted by the pupil)

What part of the eye is composed of 5 layers of neurons?

The retina - the five layers are receptors, horizontal cells, bipolar cells, amacrine cells, and retinal ganglion cells.

What is the solution to the problem that light is filtered and distorted on its way through the neuronal cell layers to the receptors?

Fovea - a specialized area of the retina with a thinning of the retinal ganglion cell layers.

Rods

Dominates in dim light. Sensitive to light, poor acuity, lack of color, referred to as scotopic vision

Cones

Dominated in ample light. High acuity, color, referred to as phototopic vision