lecture 5 cns

afferent (sensory) neurons

carry info toward CNS from receptors, long peripheral axon (PNS) and short central axon (CNS) 

efferent (motor) neurons

carry info away from CNS to effector cells (muscle, glands or neurons)

interneurons

connect afferent and efferent neurons, integrate sensory input and motor output within the CNS. (peripheral)

glial cells of CNS

support, protect, and nourish neurons (non- conducting, mitotic))

oligodendrocytes 

form myelin sheath around CNS axons

astrocytes

main “glue” of CNS, stimulate formation of tight junctions within capillaries to form blood-brain-barrier (BBB), regulated ECF, form neural scars to help repair brain injuries 

microglia

immune defense cells of CNS

ependymal cells

line fluid-filled cavities (ventricles) within brain and spinal cord, help form cerebrospinal fluid (CSF) 

cerebrum

divided into right and left cerebral hemispheres 

• connected by a massive bundle of axons = corpus collosum

• 2 hemispheres use neural connection to communicate and cooperate with each other 

occipital lobe

located in posterior region of brain

• primary visual cortex; carry out initial processing of visual input 

temporal lobe

located on lateral sides of brain 

• primary auditory cortex; receives auditory (sound) information 

• olfactory cortex 

parietal lobe 

on superior region, posterior to central sulcus; primary somatosensory cortex and somatosensory association area receives and processes sensory input

frontal lobe 

anterior region of brain, anterior to central sulcus; primary motor cortex and premotor cortex involved in voluntary motor activity, speaking ability, elaboration of thought 

broca’s area (motor speech area)

located in the left frontal lobe, regulates breathing/vocalization patterns for normal speech

• lets us use mouth, tongue, lips to shape sounds when speaking

broca’s aphasia

patients appear frustrated, insight intact (good comprehension- consciously aware of what to say); non-fluent speech (broca = broken boca)

• unable to coordinate and execute motor commands needed to produce speech - words not properly formed and speech is slow and slurred

wernicke’s area (receptive speech area)

located in left cortex at junction of parietal, temporal and occipital lobes

• concerned with language comprehension 

wernicke’s aphasia

patients do not have insight (poor comprehension- dont realize others can’t understand what they are saying)

• difficulty understanding language and unable to produce comprehensible speech 

• Wernicke is a Word salad and makes no sense 

parkinson’s disease

gradual destruction of neurons that release neurotransmitter dopamine in basal nuclei 

• basal nuclei lack enough dopamine to exert normal roles, become more active resulting in motor control issues, resting tremors, and rigidity.

thalamus

collection of large nuclei that serve as sensory relay stations for preliminary processing of sensory input 

• all sensory input synapse in thalamus on its way to cortex 

hypothalamus 

integrating center for important homeostatic functions - regulating internal environment 

• body temp, thirst, urine output, controls anterior pituitary hormone secretion, and produces posterior pituitary hormones

• serves as a major ANS coordinating center; affects all smooth muscle, cardiac muscle and exocrine gland

• controls HR and BP by regulating autonomic centers in medulla

limbic system

lobes of cerebral cortex

• limbic lobe (cingulate, dentate and parahippocampal gyri)

• amygdala, hippocampus

• basal nuclei, thalamus, hypothalamus 

• associated with: emotions, behavioral patterns, motivation, learning and memory. 

Norepinephrine (NE), dopamine (DA) and serotonin 

Linked to underlying neurophysiological mechanisms responsible for psychological observations of emotions and motivated behavior

cerebellum

important in coordinating/executing movements and controlling posture and balance

vestibulocerebellum

maintains balance and controls eye movements

spinocerebellum

enhances muscle tone and coordinates skilled, voluntary movements involving multiple joints

• makes ongoing adjustment (fine-tuning) to ensure smooth, precise directed movement

cerebrocerebellum

plans and initiates voluntary activity by providing input to cortical motor areas

brainstem

• consists of: midbrain, pons, medulla oblongata

• critical connecting link between rest of brain and spinal cord 

• all axons that relay signals between forebrain, cerebellum and spinal cord pass though 

• functions: contains centers that control cardiovascular, respiratory and digestive function and controls overall degree of cortical alertness via reticular activating system 

gray matter 

inner butterfly-shaped (h-shaped) area composed of:

• interneurons and unmyelinated axons

• cell bodies and dendrites of efferent neurons

dorsal horns

contains cell bodies of interneurons where afferent neurons terminate 

ventral horns 

contains cell bodies of efferent motor neurons supplying skeletal muscles

lateral horns

contains cell bodies of autonomic nerve fibers supplying cardiac and smooth muscle and exocrine glands

• visceral motor nuclei 

visceral motor nuclei

clusters of nerve cell bodies in the lateral horns of the spinal cord that control involuntary functions of internal organs

white matter

surrounds gray matter and grouped into 3 columns on each side of spinal cord

• organized into ascending and descending tracts that carry signals to and from the brain.

ascending tracks (white matter)

transmit afferent information from spinal cord to brain (touch, pain, temperature)

descending tracts 

carry efferent information from brain to spinal cord (movement, posture, reflexes)

afferent (sensory) pathway (Spinal Cord)

1. afferent axons carrying incoming signals from sensory receptors

2. enters spinal cord on the dorsal side through dorsal roots

3. creating sensory info such ass touch, temp, pain. 

efferent (motor) pathway (Spinal Cord)

1. efferent axons transmitting signals from the spinal cord to muscles and glands

2. exits spinal cord on the ventral side through ventral roots

3. responsible for motor control and reflex actions.

spinal nerves

at each spinal level, the dorsal and ventral roots join togehter to form a spinal nerve

• each spinal cord is “mixed” (afferent and efferent)

• this allows 2 way communication between the brain/spinal cord and the rest of the body 

reflex arc

neuronal pathway involved in accomplishing reflex activity

• 5 components: 1. sensory receptor, 2. afferent pathway, 3. integration center 4. motor neuron, 5. effector organ

1. sensory receptor 

responds to a stimulus by producing action potential

2. afferent pathway 

relays action potential toward CNS (integrating center)

3. integrating center

CNS; processes all information available to it from receptor and from all other inputs 

• “makes a decision” about appropriate response and initiates the motor response.

4. efferent pathway 

carries instructions from integrating center to effector

5. effector organ 

muscle or gland; carries out desired response

simple reflex arc

1. activation of receptor by a stimulus

2. activation of a sensory neuron 

3. information processing in the CNS

4. activation of a motor neuron (interneuron stimulates motor neurons that carry AP’s to periphery) 

5. response of a peripheral effector