Lecture 2 - Nervous Tissue pt 1

nervous tissue

initiates and transmits nerve impulses to coordinate physiological function

this is not just neurone, but also includes different cells coinciding with one another

afferent vs efferent division

afferent:

• signals coming into the CNS

• caused by sensory and visceral stimuli

efferent:

• signals coming out of the CNA

• 3 branches: somatic, autonomic, enteric

3 branches of the efferent division

• somatic. - consists of motor neurone associated with the skeletal system

• autonomic - regulates w/ homeostasis

• enteric - modulates the digestive system

PNS vs CNS

CNA - brain & spinal chord

PNS - nerve fibres carry info b/n CNS and body

central nervous system - brain & spinal chord

brain:

• cerebrum - cortex + subcortical structures

• cerebellum

• brainstem - thalamus, midbrain, pons, medulla oblongata

spinal chord:

• cervical (8 nerve pairs)

• thoracic (12 nerve pairs)

• lumbar (5 nerve pairs)

• sacrum (5 nerve pairs)

• coccygeal (1 nerve pair)

macrostructure of the brain

the brain is comprised of 4 main lobes:

1. frontal lobe

2. parietal lobe

3. occipital lobe

4. temporal lobe

frontal lobe

• located at front of head

• involved with development, personality traits, decision making, movement

• recognition of smell, contains Broca’s area, which is associated with speech ability

parietal lobe

• middle part of the brain

• involved in sensory function; i.e. pain and touch in the body

• helps identify objects and spatial relationships

• houses Wernicke’s area, which helps the brain to understand spoken language

occipital lobe

back of the brain and used for vision

temporal lobe

• sides of the brain

• involved in short-term memory, speech, musical rhythm, and some degree of smell recognition

grey matter in the CNS

• the outermost layer of the cerebrum (cortex) is grey Due to a lot of cell bodies from the neurons

• This is where informatuion is taken into neurons for processing

• Deep grey - subcortical structures: consists of really important cell bodies of neurons such as fear, memory

overall, these are neuronal cell bodies which process information

• this home to neural cell bodies, axon terminals, and dendrites , also the nerve synapses

• abundant in the cerebellum, cerebrum, and brain stem

• this forms the butterfly shape of the CNA

white matter

• myelinated axons which transmit the information

• long fibers that emanate from and connect neurons. Axons are insulated by myelin, which increases the speed of conduction. Myelin is what gives the white appearance to these fibers of the brain — hence the term "white matter." White matter integrity plays a crucial role in various neurological conditions and cognitive processes

describe the importance of the interplay between grey matter and white matter

the interplay between the gray matter of the cortex and the white matter of subcortical fibers is critical for efficient communication within the brain, facilitating higher order functions such as learning, memory, and executive control.

sulci and gyri of the brain

• sulci = trophs

• gyri = crown

• important for having more neurone in the brain

• note the precentral gyrus (frontal), postcentral gyrus (parietal), and the superior temporal

• the more S&G, the more abundant the neutrons

anatomical landmarks for functional regions in the brain

• somatosensory cortex

• primary visual cortex

• auditory cortex

• motor cortex

somatosensory cortex

• Located posterior to the central sulcus, the primary somatosensory cortex is where conscious awareness of somatosensory stimuli occurs.

• It processes information from the body, with the medial aspect receiving signals from the lower extremities and the lateral aspect from the upper extremities and face.

• This area is critical for the perception of sensory modalities, and damage can result in loss of sensation or altered sensory perception.

• The primary somatosensory cortex is also organized in a homunculus, similar to the primary motor cortex, reflecting the sensitivity of different body parts.

• The somatosensory association cortex, located posterior to the primary somatosensory cortex, analyzes and processes somatic stimuli.

• It compares new sensory information with old memories, allowing for recognition and understanding of stimuli.

• This area is essential for integrating sensory experiences and forming new memories related to touch and proprioception.

• Damage to this cortex can impair the ability to recognize objects by touch, known as astereognosis.

primary visual cortex

• The primary visual cortex, located in the posterior occipital lobe, is where we become consciously aware of visual stimuli.

• It receives visual information directly from the retina via the optic nerve, allowing for initial processing of visual data.

• This area is essential for basic visual perception, such as detecting light, color, and movement.

• Damage to the primary visual cortex can result in blindness or visual field deficits.

• Visual association cortex:

• Located anterior to the primary visual cortex, the visual association cortex analyzes and processes visual stimuli for recognition.

• It compares current visual information with past visual memories, aiding in the understanding of what we see.

• This area is crucial for higher-order visual processing, such as recognizing faces and objects.

• Damage to the visual association cortex can lead to visual agnosia, where individuals can see but cannot interpret visual information.

auditory cortex

• The primary auditory cortex is responsible for making us consciously aware of auditory stimuli, processing sounds that enter our ears.

• It is located in the superior temporal gyrus and is essential for detecting sound frequency and intensity.

• Damage to this area can lead to hearing loss or difficulty in sound localization.

• The auditory association cortex analyzes sounds and compares them to old auditory memories, helping us recognize and understand what we hear.

• It is involved in forming new auditory memories and providing meaning to sounds, such as recognizing music or speech.

• Damage to this cortex can impair the ability to understand spoken language or recognize familiar sounds.

motor cortex

• The primary motor cortex is responsible for initiating and executing voluntary muscle movements, sending motor signals down the spinal cord to skeletal muscles.

• Located anterior to the central sulcus, it plays a crucial role in controlling voluntary movements of the body.

• The medial aspect of the primary motor cortex is specifically involved in controlling movements of the lower extremities, while the lateral aspect controls movements of the upper extremities and face.

• Damage to the primary motor cortex can lead to motor deficits, highlighting its importance in voluntary movement execution.

• The organization of the primary motor cortex is often depicted in a homunculus, illustrating the proportional representation of body parts based on their motor control needs.

• The motor association cortex, located anterior to the primary motor cortex, is essential for planning and coordinating movements before they are executed.

• This area integrates sensory information and past experiences to formulate a movement plan, distinguishing it from the primary motor cortex, which executes the plan.

• Damage to this area can result in difficulties with movement planning, even if the primary motor cortex is intact.

• The motor association cortex is involved in complex movements that require coordination of multiple muscle groups.

note the subcortical structures of the brain

• cingulate cortex

• mamillary body

• hypothalamus

• amygdala

• hippocampus

• fornix

• thalamus

parasympathetic

• pupil - constrict

• heart - slow heartbeat

• airways - constricts bronchial tubules

• liver - stimulates bile release

• digestive system - stimulates activity

• uterus - relaxation

• urinary system - increases urinary output

• blood vessels constrict

this dominates when you are at rest. most of the signals travels down the vagus nerve, which Is the longest cranial nerve in the body. it runs from the brainstem through the neck and chest, into the abdomen, touching the heart, lungs, and intestines along the way

sympathetic

• pupil - dilate

• heart - increased heart beat

• airways - dilates bronchial tubules

• liver - increases rate of glycogen to glucose

• digestive system - decreased activity

• uterus - vaginal contraction

• urinary system - release bladder

• stimulated secretion in the sweat gland

• adrenal glands produce adrenaline