Nervous system- Lecture 2 Flashcards
What is the definition of Behaviour? With explanations.
An Organisms internally coordinated responses to its internal/external environment.
REGISTER= Sense information from its environment. (example, magnetic fields)
INTERNAL CHANGE/TRANSFORMATION/PROCESSING of information. (example, sensing under anaesthesia)
GENERATE= Appropriate responses. (example, paralysis. these limit certain types of behaviour, not behaviour as a whole)
What are the Differences between Single cell organisms and complex organisms behaviour?
Single Cell Organism:
-Registration: molecule attaches itself to a cell membrane
-Transformation: chemical change leads to cascade of chemical changes in cell.
-Response generation: DIRECTLY results in particular behaviour.
Complex cell:
-Same registration as single cell
-Same transformation, however, this results in chemical changes in OTHER cells, generating nerve impulses, which is transmitted along specific neural pathways. [CASCADE OF CASCADES: Communication]
-Response generation: EVENTUALLY resulting in activation of output systems, causing the execution of a particular movement
What is a Nervous system?
-A network of electro-chemically active cells (neurons)
-specialized to communicate with each other
Describe the different parts of the Peripheral nervous system
Somatic Nervous system: skeletal muscles, [voluntary control]
Autonomic NS: Parasympathetic, rest and maintenance
Sympathetic, fight or flight
-outputs are muscles and glands [involuntary control]
Explain the Monosynaptic reflex arc
- Activate sensory neuron when muscle is stretched
- Axons enter spinal cord via dorsal root
- Connect directly with motor neuron
- Axons exit spinal cord via Ventral root
- Activate same muscle from which signals originated
- Causes this to contract
Monosynaptic definition: There is only 1 connection between the Sensory and Motor Neuron. [but other connections can add on top of these neurons, just not in between.]
Explain the Polysynaptic reflex arc
- Sensory and motor neurons are connected via one/more INTERNEURONES (relay neurons)
- Receptor and effector are in different places, for example: the Withdrawal reflex. [when you step on a pin you take your leg off]
- More flexible arrangement, can show simple forms of learning.
The spinal cord neurons can generate complex movement patterns, such as walking, but what is a LIMITATION of these neurons?
They cannot voluntarily initiate Movements.
-Patterns are only elicited in response to appropriate stimulation.
-Anything more complex than that will Require a brain.
Explain what happens from the Periphery.
- Detection and transmission of sensory signals. - Specialised receptor cells respond to changes in the environment.
- Mostly not neurons, but directly connected to a sensory neuron.
Interlude- change detection.
What is a Nervous system used for?
To interact flexibly with the environ-
ment:
register (‘sense’) the environment;
transform (interpret, ‘make sense
of’) those signals;
generate an appropriate response.
Describe the basics of the Nervous system
network of electro-chemically active cells, specialised to communicate with each other
Even structurally simple animals have centralised NS (e.g., flatworm, leech, insect) with separate:
CNS (“proto-brain” & nerve cord)
& PNS: (peripheral nerves)
Describe the Structual and Functional Nervous system of Vertebrates
NS of vertebrates similar, but more complex:
Structural: central & peripheral NS more clearly separated
Functional: more hierarchically organised, with brain specialized to organize &
direct communication between neurons control actions of (distant) body parts
Describe the Monosynaptic Reflex Arc (e.g., knee-jerk reflex)
- Inside each muscle fibre, specific sense organs (muscle spindles) activate a sensory
neuron when muscle is quickly stretched - Their axons enter spinal cord (via dorsal root), connecting directly with
- Motor neurons, which send their axons out (via ventral root),
- activating the same muscle from which signals originated (causing it to contract).
a) Through the body, monosynaptic reflexes work to ‘resist’ or ‘dampen’ quick
stretching of skeletal muscles, enabling smooth, stable movement;
b) Even a monosynaptic reflex can have additional synaptic connections (see inset)
Define, and Describe the structural and functional aspects of a Synapse.
INTERLUDE: Synaptic Connections
Synapse = signalling link between a neuron and another cell (e.g., another neuron)
Structural (i.e., physical):
-The place where the specialized ‘sender’ part of a neuron comes close the specialized ‘receptor’ part of the target cell
-Two neurons typically share many of these places, i.e., they have many synapses:
Functional (i.e., more abstract):
No matter how many such ‘contact points’ are between two neurons, they all con-
tribute to the same signal
That is, they function as one synapse:
Monosynaptic: functionally, only one synapse linking sensory & motor neuron
Polysynaptic: functionally, several synapses between sensory & motor neuron
more accurate: bi-synaptic (2 synapses), tri-synaptic (3 synapses), poly-
synaptic
=> Learning = modifying links between inputs and responses
Describe Central Pattern generators [Eg) the spinal cord]
Spinal cord neurons can even generate complex movement patterns (e.g., walking –
see stepping reflex in young infants),
but cannot voluntarily initiate movements – patterns are only elicited in response to
appropriate stimulation!
a) Experimental evidence: cat with spinal cord resection walking on treadmill
