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Nervous and Sensory Systems - Coggle Diagram
Nervous and Sensory Systems
Structure and Function of Nervous System
Controls, coordinates and integrates all body activities
Regulates and maintains homeostasis
Fast acting and communicates with cells by electircal impulses
Sensory and Motor Input Integration
Receives sensory input from brain
Nervous system processes and inteprest situation to determine how to react (integration)
Activates effector muscles which triggers an action (motor output)
Cells of Nervous System
Nerve tissue contains neurons
Are structural units of nervous system
Consists of cell body, soma, with extensions called an axon and one or more extensions called dendrites
Dendrites receive electrical nerve impulses and conduct them toward the cell body and axon
Axons conduct nerve impulses away from the cell body and most neurons have a single axon arising from axonal hillock on cell body
CNS neurons are able to to replace thenmselves if i jured or destroyed barring a few exceptions
Types of neurons
Sensory (afferent) conduct action potentials towards CNS and detect internal and external environments and facilitate motor coordination
Motor (efferent) conduct action potentials away from the CNS towards muscles or glands
Interneurons conduct action potentials within the CNS from one neuron to another , mainly between sensory and motor neurons
Neuroglia supports functions of neurons
Neuroglia comprise almost half the brain and spinal cord tissue and much more numerous than neurons
Support, nourish and protect neurons
Certain neuroglia wrap around axons of neurons to create a myelin sheath
Cell Membrane potential
surface is usually electrically charged (polarized) compared with its inner contents. This is due to unequal amounts of positive and negative ions.
An action potential is a change in neuron membrane polarization and a return to its resting state.
n action potential forms a nerve impulse propagated along an axon.
How do neurons communicate
Sypnases
Axodendritic synapses are those between the axon endings of a neuron and the dendrites of other neurons.
Axosomatic synapses are those between axon endings of one neuron and soma of others.
Sypnase between a neuron and muscle cell is called a neuromuscular junction
Presypnatic neuron carries impulse into sypnase
Postsypnatic neuron receives sypnase through sypnastic transmission
Junction between two communicating neurons is called sypnatic cleft
Chemical sypnases receive and release chemical neurotransmitters
Electrical sypnases are less common and allow for rapid transmission across electrical sypnases
actions of neurotransmitters include effects on sleeping, anger, thinking, hunger, movement, memory, and many other functions.
Synaptic transmission is commonly affected by either the enhancing or inhibiting effects of neurotransmitters, their destruction, or the blocking of receptor binding.
Anything that reduces neurotransmitter activity may slow the brain’s ability to communicate with the rest of the body.
Central nervous system (CNS)
Consists of brain and spinal cord, located in dorsal body cavity and is the control centre of nervous system
Receivs information from and sends info to body
Key decision maker
Brain
Surrounded by firtly grey matter full of neuron cells bodies then white matter full of myelinated fiber tracts
Btwn bony coverings and soft tissues lays the meninges which are layered membranes that protect brain asn spinal cord
cerebrospinal fluid surrounds brain and helps maintain stabel ionic concentration, cushions brain and noursih brain
Blood brain barrier allows to selectively allow specific molecules to pass and to keep others from reaching brain
Spinal Cord
Spinal cord is a thin column of nerves leading brain to the vertebral canal
Contains spinal reflex
Peripheral Nervous System (PNS)
consists of peripheral nerves connecting CNS to other parts of the bodies
Divided into sensory and motor divisions
Allows us to process infobetween our bodies and our environments
Somatic nervous system oversees conscious activities
Autonomic nervous system oversees unconsious activities
Sensory receptors are specialised to respond to stimuli and types include Chemoreceptors, Mechanoreceptors, Nociceptors, Thermoreceptors-
General senses of touch, pressure, temp and pain are spread throughout the body via muscle, joint, skin, and visceral receptors and two types are nonencapsulated (free), encapsulated
Reflex is defined as fast, automatic response to a specific stimulus and reflex activity in human body are either inborn or learned
Inborn are rapid and predictable motor responses to stimuli that are formed between neurons during human development
involuntary and subconsciously maintain body posture, help to avoid pain, and control visceral activities
n a reflex arc, sensory impulses from receptors can reach their effectors without being processed by the brain. Some reflex arcs use interneurons. The five basic components of a reflex arc are a receptor, a sensory neuron, an integration center, a motor neuron, and an effector.
Effects of ageing on nervous system
Risk of stroke
Fatty deposits accumulate in blood vessels, there is decrease in blood flow to the brain
Can increase chances that an affected vessel will rupture leading to symptoms of strokes
Slower reaction time
Bcos brain processes nerve impulses more slowly,
Person who exercises loses less nerve cells in brain
Overconsumption of alcohol daily reduces brain function
Loss of neurons
neuronal loss occurs and some neurons shrink
cause decrease in brain size and weight
Neuroglia Increase and Deposits
Brain neurons accumulate abnormal intracellular deposits. Extracellular plaques may affect memory processing. When deposits and plaques exceed normal amounts caused by aging, clinical abnormalities may occur.
These particular changes are also characteristic of the brains of those with Alzheimer’s disease
Changes in transmission efficiency
Lower number of functional nerve cells
Fewer nerve cells result in more space to cross, and the coherence of the message may be disrupted, or random background noise (neural noise) could interfere with the clarity of the message.
Anatomy and Function of Sensory Systems
Olfaction- Sense of smell
Mechanism for sense of smell concerns olfactory receptors
Olfactory recpetors have hair like cilia which help to differentiate odors
Odorant molecules must partially condensate from gases to fluids before receptors can detect them. Impulses are analyzed by olfactory bulbs and interpreted in the olfactory complex of the brain.
Gustatory- Sense of taste
Taste pores have tiny projections called taste hairs, which are the sensitive parts of the taste receptor cells. Stimulation triggers an impulse on a nearby nerve fiber traveling to the brain.
The five primary taste sensations are sweetness, sourness, saltiness, bitterness, and umami (deliciousness).
Auditory- Sense of hearing
Serves two sensory of detecting sound and body position
External ear
Auricle (pinna): A funnel-shaped structure composed of elastic cartilage, thin skin, and small amounts of hair; most people refer to this structure as “the ear.” The auricle functions to funnel sound waves to the external acoustic meatus
External acoustic meatus. Glands secrete cerumen, a yellow-brown waxy substance commonly referred to as earwax. Cerumen helps to trap foreign particles and repel insects from entering the ear.
Eardrum (tympanic membrane): A semitransparent membrane covered by thin skin on the outside and mucous membrane on the inside that actually
moves back and forth in response to sound waves; it is the boundary between the outer and middle ear.
Middle Ear
The middle ear (tympanic cavity) inside the petrous portion of the temporal bone is filled with air and contains the auditory ossicles (the malleus, incus, and stapes). These bones are attached to the tympanic cavity wall by ligaments and bridge the eardrum and inner ear to transmit vibrations
Vibrations are passed to the auditory ossicles, which is held to an opening
(the oval window) by ligaments. Vibration of the stapes moves fluid within the inner ear to stimulate hearing receptors
Inner ear
The internal ear is complex, with chambers and tubes forming the bony labyrinth.
Inside the labyrinth structures are three semicircular canals, which aid in equilibrium, and a cochlea, which functions in hearing.
The vestibule and its two expanded chambers (the utricle and saccule),with a tiny macula containing many sensory hair cells function in equilibrium.
When the head is upright, the hairs project upward into a gelatinous material. When the head bends forward, backward, or to one side, the hairs bend to signal nerve fibers.
The organs of dynamic equilibrium are the three semicircular canals in the labyrinth. A swelling called an ampulla houses sensory organs, each known as a crista ampullaris. Hair cells within a cupula are bent to signal the brain.
Visual-Sense of sight
Important for maintenance and protection of eyes
Protect, lubricate, move eye
Accessory structures include eyebrows, eyelids and conjunctiva
