Tissues (1)
- Created by: Sophieparkinson19
- Created on: 02-01-21 01:54
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- Nervous Tissues
- Three Overlapping Functions
- Sensory Input: Monitor changes via sensory receptors
- Integration: Processes and interprets sensory input
- Motor Output: Initiates a response via effector organs (muscle and glands)
- Two Parts of Nervous System
- Central Nervous System (CNS): Brain and Spinal cord.
- Peripheral Nervous System (PNS): Consists of bundles of nerves that extend from the brain and spinal cord
- Peripheral Nervous System
- Consists of Two Main Parts
- Somatic Nervous System (SNS- Voluntary)- allows conscious control of skeletal muscles.
- Autonomic Nervous System (ANS- Involuntary)- visceral motor fibres that regulate the activity of smooth and cardiac muscle and glands.
- Two further subdivisions: Sympathetic, Parasympathetic
- Typically work in opposition (e.g. if one stimulates, the other inhibits.
- Two further subdivisions: Sympathetic, Parasympathetic
- Two Further Subdivisions
- Sensory (Afferent) division: conveys impulses to the CNS via somatic or visceral afferent fibres.
- Motor (Efferent) division: transmits pulse from the CNS to effector organs
- Consists of Two Main Parts
- Neurons
- Highly specialized cells that conduct messages to and from one part of the body to another
- Extreme longevity- can last 100+ years
- Amitotic- lost their ability to divide
- Exceptionally high metabolic rate
- Dendrites provide an enormous surface area for receiving signals from other neurons. They convey messages toward the cell body.
- Signals are not action potential but are short
- Xons single process that originates from axon hillock and ends at synaptic knob
- Nerve impulses release neurotransmitters into the extracellular space
- Myelin Sheath
- Myelinated fibers conducts nerve impulses rapidly
- Exceptionally good electrical insulation
- They are formed by Schwann cells that wrap themselves around nerve fibres, squeezing out their cytoplasm util many concentric layers of plasma membrane enclose the axon
- Gaps in between adjacent Schwann cells are celled Nodes of Ranvier
- Important in face impulse transmission
- Muscle Tissue
- Skeletal Muscle (Voluntary): Organs that attach and cover the bony skeleton
- Cardiac Muscle (Involuntary) : Occurs only in the heart, constitutes the bulk of the heart walls
- Smooth Muscle (Involuntary): Found in the walls of hollow visceral organs where it is used to force liquids and other substances through internal body channels.
- Skeletal Muscle
- Discrete organ made up of several kinds of tissues:
- Muscle Fibers
- Blood Vessels
- Connective Tissue
- Nerve Fibers
- Components of Skeletal Muscle
- Each muscle fiber contains myofibrils that run parallel to its length
- Sarcomeres contain each small structure called myofilaments which are made up of:
- Myosin (thick filaments)
- Actin, Tropomyosin, and Troponin (thin filaments)
- Regulation of Skeletal Muscle Contractions
- Sarcoplasmic Reticulum: elaborate ER that surrounds each myofibril, running longitudinally and communicating at the H-zone
- T-tubules: at each A band/ I band junction the sarcolemma of the muscle cell protrudes deep into the cell interior forming elongated T-tubules
- Electrical impulses from nerves travel along the sarcolemma and into T-tubules whih reach deeply into muscle cell and to every sarcomere.
- These impulses signal the release of calcium, causing muscle fibre contraction at the same time
- Sliding Filament Model of Contraction
- During contraction, the thin filament slide past the thick ones so that the actin and myosin overlap to a greater degree.
- Myosin heads latch onto myosin-binding on the actin- cross bridge
- Sliding begins and these heads detach and reattach several times during concentration.
- The muscle cell shortens: Z-discs are pulled toward the M line and I band shorten.
- Discrete organ made up of several kinds of tissues:
- Three Overlapping Functions
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