Week 3: Heart Beat Control

Question 1

There are other examples of CPG other than

Answer 1

locomotion in lamprey like control the heartbeat of leeches

Question 2

The heartbeat control system of

Answer 2

medicinal leech has been studied intensively for over three decades

Question 3

The leech has two tubular hearts running the

Answer 3

length of the body and moving blood through its closed circulatory system

Question 4

The beating pattern of leeches (beat period of 4 to 10s) is asymmetric with one heart and the other… (2)

Answer 4

with one heart generating high systolic pressure through a front-directed peristaltic wave (peristaltic coordination mode) along its length]

, and the other generating low systolic pressure through near-synchronous constriction (synchronous coordination mode) along its length.

Question 5

The peristaltic heart moves

Answer 5

blood forward,

Question 6

As compared to peristaltic heart, the synchronous heart has been hypothesized mainly to

Answer 6

push blood into the peripheral circulation and supports rearward (towards the back) blood flow

Question 7

After descriving peristaltic and synchronous

After about 20 – 40 beats (switch period ~100 – 400 s)

Answer 7

the hearts switch roles

Question 8

The two heart tubes leech has receives which is located in (2)

Answer 8

excitatory input from an ipsilateral member of a pair of segmental heart (HE) motor neurons,

located in each midbody segmental ganglion,

Question 9

The firing pattern of heart motor neurons (i.e., fictive motor pattern is (2)

one side firing while other side

Answer 9

bilaterally asymmetric, with motor neurons on one side firing with a rear-to-front progression

while those on the other side fire nearly synchronously with appropriate side-to-side coordination of these two firing patterns (they swithc)

Question 10

The heart motor neurons are controlled and coordinated by the heartbeat CPG through

Answer 10

rhythmic inhibitory drive (period 5-12 s).

Question 11

Nine pairs of identified segmental heart (HN) interneurons (plus one pair of unidentified pair) compose the

Answer 11

CPG

Question 12

The core CPG consists of

index (2)

Answer 12

seven pairs of these interneurons located in
the first seven midbody ganglia of the nerve cord and are indexed by ganglion number and body side (HN(L,1) – HN(R,7))

Question 13

Rhythmic activity in the CGP network is paced by a

Answer 13

highly interconnected timing network consisting of coordination (HN(1) and HN(2) interneurons) and oscillator interneurons (HN(3) and HN(4) interneurons).

Question 14

The firing pattern of the interneurons (and particularly of the front (HN(3) and
145 HN(4)) and the middle (HN(6) and HN(7)) premotor interneuron) of this core CPG has been

Answer 14

extensively characterized and is also bilaterally asymmetric like that of
147 the heart motor neurons and with appropriate side-to-side coordination.

Question 15

The asymmetry in firing patterns is not permanent, however; there are regular (every 200-400 s) side-to-side switches in the CGP network

Answer 15

peristaltic and synchronous patterns in the heart interneurons that underlie
the changes in both the motor pattern and the rhythmic constriction patterns of the heart tubes.

Question 16

These switches in coordination are mediated by the HN(5) switch interneurons in CGP network

Answer 16

which link the timing network to the middle premotor interneurons by bilateral inhibitory connections; only one of this pair of interneurons is rhythmically active at a time the other is silent.

Question 17

Premotor interneurons and motor neurons on the side of the active switch interneuron are coordinated synchronously, while

Answer 17

those on the on the side of the silent switch interneuron are coordinated peristaltically.

Question 18

Order of explaining new CPG (15)

Answer 18

1. Leech has 2 hearts
2. Beating pattern, peristaltic and other synchronous
3. Peristaltic heart…
4. Synchronous heart ….
5. After 20-40 heart beat….(switch)
6. Two heart receive excitation from HE motor neurons
7. HE firing pattern
8. HE controlled via heartbeat CPG through….
9. 9 pairs of HN compromise heartbeat CGP
10. Core CGP consist of
11. Rhythmic activity in CGP network paved by…
12. Firing pattern of HN neurons
13. Asymmetry not permanent
14. Switched in CGP that are mediated by..
15. Pre motor interneurons

Question 19

The heartbeat central pattern generator (CPG) in medicinal leeches controls blood flow

This circuit (2)

Answer 19

within a closed circulatory by programming the constrictions of two parallel heart tubes

This circuit reliably produces a stereotyped fictive pattern of activity and has been extensively characterized.