C13 Nervous System Flashcards
Central Nervous System (CNS) consists of
brain and spinal cord
Peripheral Nervous System (PNS) consists of…
all neurones that connect CNS to rest of body. These are the sensory neurones, carry nerve impulses from receptors to CNS, and motor neurones (which carry nerve impulses away from CNS to the effectors).
Functional Organisation
(Somatic Nervous System)
under conscious control (used when you voluntary decide do something. SNC carries impulses to the body’s muscles.
Functional Organisation
(Autonomic Nervous System)
works constantly. Under subconscious control and used when body does something automatically without you deciding to do it (involuntary). E,g heart beat or digest food. ANS carries nerve impulses to glands, smooth muscle and cardiac muscle.
ANS further divided by function into…
Sympathetic and parasympathetic nervous system.
Sympathetic nervous system
Sympathetic nervous system: if the outcome increases activity (increase HR).
Parasympathetic nervous system:
Parasympathetic nervous system: if the outcome decreases activity (decrease HR or breathing after exercise).
Mechanoreceptors
Detect movement, pressure and tensions, e.g sound
Chemoreceptors
Detect chemical stimuli, e.g taste and smell
Thermorecptors
Detect temperature change, e,g in the skin, the hypothalamus
Electroreceptors
detect electrical fields (mainly found in fish)
Photoreceptors
detect light and some other form of electromagnetic radiation, e.g bees detect UV light.
Role as a Transducer
sensory receptors detect range different stimuli. The receptor converts the stimulus into nerve impulse, called a generator potential.
Neurones role
role to transmit electrical impulses rapidly around body, so it can respond changes in its internal and external environment.
Structure of a Neurone:
Cell body
contains nucleus surrounded by cytoplasm. In cytoplasm large amounts ER and mitochondria which involved production neurotransmitters (chemicals which used to pass signals from one neurone to next).
Structure of a Neurone:
Dendron
short extensions, come from cell body. Extensions divided into smaller and smaller branches known dendrites, responsible transmitting electrical impulses towards cell body.
Structure of a Neurone:
Axons
singular, elongated nerve fibres, transmit impulses away from cell body. Can be very long. Fibres cylindrical in shape, consisting very narrow region cytoplasm surrounded by plasma membrane.
Skeletal Muscle
responsible for movement, usually attached to bone, make up bulk of body’s muscle tissue.
Cardiac Muscle
found only in the heart, myogenic meaning they are self stimulating causing a continuous rhythm.
Involuntary/Smooth Muscle:
found in many parts of the body such as walls of hollow organs such as bladder and stomach, and in vessels such as arteries and digestive tract.
Skeletal muscles
-Fibre appearance
-Control
-Arrangement
-Contraction speed
-Length of contraction
-Structure
-Striated
-Conscious (voluntary)
-Regularly arranged so muscle contracts in one direction
-Rapid
-Short
Cardiac muscle:
-Fibre appearance
-Control
-Arrangement
-Contraction speed
-Length of contraction
-Structure
-Specialised striated
-Involuntary
-Cells branch and interconnect resulting in simultaneous contraction
-Intermediate
-Intermediate
-Cardiac muscles does show striations but they are much fainter than those in skeletal muscles. Fibres are branched and uninucleated.
Involuntary Muscles
-Fibre appearance
-Control
-Arrangement
-Contraction speed
-Length of contraction
-Structure
-Non-striated
-Involuntary
-No regular arrangement- different cells can contract in different directions
-Slow
-Can remain contracted for relatively long period of time
-Muscles show no cross striations are called non-striated or unstriped muscles. Fibres are spindle shaped and uninucleated.
Types of neurones
sensory
motor
relay
relay neurones
transmit impulses between neurones, e.g between sensory neurones and motor neurones. They have many short axons and dendrons.
sensory neurones
carries nerve impulses from a sense organ to CNS. Has a long dendron and shorter axon than motor neurone.
motor neurone
carries impulse from the CNS to effector muscle or glands, it’s cell body lies with the CNS.
what are the stages of a nervous response to a stimuli?
Stimuli —> Receptor —> Sensory —> Relay —> Motor —> Effector —> Response
Axons of some neurones covered in a myelin sheath (made many layers plasma membrane).
how does this come to be?
-Special cells, Schwann cells, produce layers by growing around axon many times, forming a double layer of phospholipid bilayer laid down each time they grow round.
what do myelin sheaths act as, and how?
-Myelin sheath acts insulating layer, allows these myelinated neurones to conduct electrical impulses much faster than unmyelinated neurones.
-Between adjacent Schwann cells there’s small gap known as ‘a node of Ranvier’ (creates gaps in myelin sheath)
-In myelinated neurones,electrical impulse can jumps from one node to the next (transmitted much faster),
how is the brain protected?
Brain protected by skull, and initially surrounded by protective membrane (meninges).
Cerebrum
controls voluntary actions, i.e learning, memory, personality and conscious thought.
Cerebellum
controls unconscious functions, i.e posture, balance, and non-voluntary movement.
Medulla Oblongata
used in autonomic control, i.e controls HR and breathing rate.
Hypothalamus
regulatory centre for temp and water balance.
Pituitary Glands
stores and releases hormones that regulate many body functions.
Cerebrum function
-Receives information, interprets it, and then sends an impulse along motor neurons to effector organs to produce a response.
-Responsible for controlling all conscious responses and some involuntary responses.
-Many folds in the cerebrum mean there is increased surface area, and therefore increased capacity for activity.
-Each hemisphere controls the opposite side of the body.
-The cerebrum can be divided into four lobes.
Cerebellum function / role
-This area is concerned with muscular movement, posture and balance,
-It does not initiate, but coordinates.
-This means damage to the cerebellum can lead to jerky and uncoordinated movement.
Medulla Oblongata function / role
Contains many important regulatory centres for autonomic nervous system.
Controls unconscious and reflex actions.
Hypothalamus function / role
-Main controlling region for the autonomic nervous system - with a centre for both sympathetic and parasympathetic systems.
-Controls complex behaviour patterns such as feeding, sleeping and aggression.
-Monitors the composition of blood plasma.
-Produces hormones.
Pituitary Gland function / role
-Controls most of the glands in the body, and has two sections.
-Anterior Pituitary Gland - produces 6 hormones including FSH which is involved in reproduction and growth.
-Posterior Pituitary Gland - stores and releases hormones produced by the hypothalamus such as ADH.
